/* Crisp Daylight Technical: slate canvas, white elevated cards, cobalt actions, emerald
   success, amber warnings, and dark IDE surfaces for code. Legacy token names (--green,
   --acid, --orange, --paper, --white) stay so every module keeps working; the semantic
   aliases below are preferred in new code. */
:root {
  --paper: #f8fafc;
  --white: #ffffff;
  --surface-raised: #f1f5f9;
  --surface-hover: #e2e8f0;
  --ink: #0f172a;
  --muted: #475569;
  --subtle: #5b6b80;
  --lede: #334155;
  --line: #e2e8f0;
  --line-strong: #cbd5e1;
  --green: #2563eb;
  --primary-strong: #1d4ed8;
  --primary-soft: #eff6ff;
  --on-accent: #ffffff;
  --acid: #10b981;
  --emerald-ink: #047857;
  --emerald-soft: #ecfdf5;
  --orange: #d97706;
  --warning-ink: #b45309;
  --warning-surface: #fffbeb;
  --panel-green: #0f172a;
  --panel-ink: #e2e8f0;
  --panel-muted: #94a3b8;
  --code-bg: #0f172a;
  --code-bar: #0b0f19;
  --code-line: #1e293b;
  --code-ink: #e2e8f0;
  --code-muted: #8391a7;
  --code-keyword: #c084fc;
  --code-string: #fbbf24;
  --code-name: #60a5fa;
  --code-type: #2dd4bf;
  --code-number: #f472b6;
  --code-comment: #94a3b8;
  --code-pass: #34d399;
  --grid-line: rgba(148, 163, 184, 0.14);
  --grid-major: rgba(148, 163, 184, 0.22);
  --primary: var(--green);
  --success: var(--acid);
  --warning: var(--orange);
  --radius-sm: 6px;
  --radius: 10px;
  --radius-lg: 14px;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, 0.05);
  --shadow-md: 0 1px 2px rgba(15, 23, 42, 0.04), 0 8px 24px -6px rgba(15, 23, 42, 0.1);
  --shadow-lg: 0 2px 4px rgba(15, 23, 42, 0.04), 0 22px 48px -12px rgba(15, 23, 42, 0.22);
  --ring: 0 0 0 3px color-mix(in srgb, var(--green) 28%, transparent);
  --mono: 'IBM Plex Mono', ui-monospace, SFMono-Regular, Menlo, monospace;
  --sans: 'Inter', 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --sidebar-width: 240px;
}
html[data-theme='dark'] {
  --paper: #0b0f19;
  --white: #111827;
  --surface-raised: #1e293b;
  --surface-hover: #334155;
  --ink: #f8fafc;
  --muted: #94a3b8;
  --subtle: #8391a7;
  --lede: #cbd5e1;
  --line: #1e293b;
  --line-strong: #334155;
  --green: #60a5fa;
  --primary-strong: #93c5fd;
  --primary-soft: rgba(59, 130, 246, 0.16);
  --on-accent: #0b0f19;
  --acid: #34d399;
  --emerald-ink: #6ee7b7;
  --emerald-soft: rgba(16, 185, 129, 0.16);
  --orange: #fbbf24;
  --warning-ink: #fcd34d;
  --warning-surface: rgba(245, 158, 11, 0.14);
  --panel-green: #0d1321;
  --grid-line: rgba(100, 116, 139, 0.12);
  --grid-major: rgba(100, 116, 139, 0.2);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 1px 2px rgba(0, 0, 0, 0.3), 0 10px 28px -8px rgba(0, 0, 0, 0.55);
  --shadow-lg: 0 2px 4px rgba(0, 0, 0, 0.3), 0 24px 56px -12px rgba(0, 0, 0, 0.7);
}
* {
  box-sizing: border-box;
}
/* Components that set display must still disappear when hidden. */
[hidden] {
  display: none !important;
}
html {
  -webkit-text-size-adjust: 100%;
}
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 15px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: 'cv11', 'ss01';
}
::selection {
  background: color-mix(in srgb, var(--green) 24%, transparent);
}
button,
input,
textarea,
select {
  font: inherit;
}
button,
a,
input,
textarea,
select {
  -webkit-tap-highlight-color: transparent;
}
button {
  cursor: pointer;
  color: inherit;
}
/* Selects draw their own chevron so it sits clear of the right edge. */
select {
  -webkit-appearance: none;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%2364748b' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  background-size: 15px;
  padding-right: 38px !important;
}
a {
  color: inherit;
  text-decoration: none;
}
button:focus-visible,
a:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible,
summary:focus-visible {
  outline: 2px solid var(--green);
  outline-offset: 3px;
}
button:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}
input::placeholder,
textarea::placeholder {
  color: var(--subtle);
  opacity: 1;
}
h1,
h2,
h3,
h4,
p {
  margin: 0;
}
h1,
h2,
h3 {
  font-weight: 600;
  line-height: 1.15;
  letter-spacing: -0.025em;
}
h1 {
  font-size: clamp(36px, 4.2vw, 60px);
  font-weight: 700;
  line-height: 1.06;
  letter-spacing: -0.03em;
}
h2 {
  font-size: 28px;
}
h3 {
  font-size: 20px;
  letter-spacing: -0.015em;
}
p {
  max-width: 70ch;
}
small {
  font-size: 12px;
}
code,
pre,
kbd {
  font-family: var(--mono);
}
code {
  font-size: 0.86em;
  background: var(--surface-raised);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 1px 5px;
}
pre {
  padding: 20px 22px;
  background: var(--code-bg);
  color: var(--code-ink);
  border: 1px solid var(--code-line);
  border-radius: var(--radius);
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  line-height: 1.75;
  font-size: 13px;
  box-shadow: var(--shadow-sm);
}
pre code {
  padding: 0;
  background: none;
  border: 0;
  font-size: inherit;
}
/* Python highlighting (highlight.js) on dark code surfaces, in both themes. */
.tok-keyword {
  color: var(--code-keyword);
}
.tok-function,
.tok-decorator {
  color: var(--code-name);
}
.tok-type {
  color: var(--code-type);
}
.tok-string {
  color: var(--code-string);
}
.tok-number,
.tok-constant {
  color: var(--code-number);
}
.tok-comment {
  color: var(--code-comment);
  font-style: italic;
}
svg {
  max-width: 100%;
}
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}
.skip-link {
  position: fixed;
  top: -60px;
  left: 20px;
  z-index: 100;
  background: var(--green);
  color: var(--on-accent);
  border-radius: var(--radius-sm);
  padding: 10px 14px;
  font-weight: 600;
}
.skip-link:focus {
  top: 10px;
}

/* ---------------------------------------------------------------------------
   App shell: white navigation rail and a frosted, sticky top bar
   --------------------------------------------------------------------------- */
.sidebar {
  position: fixed;
  inset: 0 auto 0 0;
  width: var(--sidebar-width);
  background: var(--white);
  border-right: 1px solid var(--line);
  padding: 22px 14px 18px;
  display: flex;
  flex-direction: column;
  z-index: 20;
  overflow-y: auto;
}
.brand {
  display: flex;
  gap: 11px;
  align-items: center;
  padding: 2px 8px;
  font-size: 15px;
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.01em;
}
.brand-mark {
  width: 34px;
  height: 34px;
  flex: none;
  color: var(--ink);
}
.brand-mark svg {
  width: 100%;
  height: 100%;
  display: block;
}
.brand-mark .brand-core {
  fill: var(--green);
}
.brand-caption {
  display: block;
  font: 500 10px var(--mono);
  letter-spacing: 0.04em;
  margin-top: 5px;
  color: var(--subtle);
}
/* Phone-only parts of the shell; the phone layout shows them. */
.topbar-brand,
.phone-bar,
.phone-scrim,
.sheet-handle,
.sheet-close {
  display: none;
}
.sheet-head,
.sheet-settings {
  display: contents;
}
.sidebar-caption {
  font: 500 10px var(--mono);
  letter-spacing: 0.1em;
  color: var(--subtle);
  margin: 34px 10px 10px;
}
.nav-link {
  display: flex;
  gap: 12px;
  padding: 9px 12px;
  margin: 3px 0;
  border-radius: var(--radius-sm);
  align-items: center;
  font-size: 14.5px;
  font-weight: 500;
  color: var(--muted);
  border: 1px solid transparent;
  transition:
    background 0.15s,
    color 0.15s;
}
.nav-symbol {
  width: 20px;
  height: 20px;
  display: grid;
  place-items: center;
  flex: none;
}
.nav-symbol svg {
  width: 19px;
  height: 19px;
}
.nav-link:hover {
  background: var(--surface-raised);
  color: var(--ink);
}
.nav-link.active {
  background: var(--primary-soft);
  color: var(--green);
  border-color: color-mix(in srgb, var(--green) 22%, transparent);
  font-weight: 600;
}
.sidebar-bottom {
  margin-top: auto;
  padding: 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  background-image:
    linear-gradient(var(--grid-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
  background-size: 14px 14px;
}
.eyebrow {
  font: 500 11px var(--mono);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--subtle);
}
.storage-badge {
  font: 10px/1.5 var(--mono);
  display: flex;
  gap: 7px;
  align-items: flex-start;
  color: var(--muted);
}
.storage-badge span {
  /* Center the dot on the first line when the label wraps. */
  margin-top: calc((1.5em - 6px) / 2);
}
.storage-badge span {
  width: 6px;
  height: 6px;
  background: var(--acid);
  border-radius: 100%;
  flex: none;
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--acid) 22%, transparent);
}
.sidebar-bottom .text-link {
  font-size: 12px;
  margin-top: 10px;
  display: inline-block;
  color: var(--green);
}
.workspace {
  margin-left: var(--sidebar-width);
  position: relative;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
.topbar {
  position: sticky;
  top: 0;
  z-index: 15;
  height: 68px;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--white) 86%, transparent);
  backdrop-filter: blur(12px) saturate(1.4);
  -webkit-backdrop-filter: blur(12px) saturate(1.4);
  display: flex;
  align-items: center;
  gap: 18px;
  padding: 0 32px;
}
.breadcrumb {
  font: 500 12px var(--mono);
  letter-spacing: 0.05em;
  white-space: nowrap;
  color: var(--muted);
}
.breadcrumb span {
  padding: 0 10px;
  color: var(--line-strong);
}
.breadcrumb strong {
  font-weight: 600;
  color: var(--ink);
}
.search-form {
  margin-left: auto;
  display: flex;
  gap: 8px;
  align-items: center;
  color: var(--subtle);
  background: var(--surface-raised);
  border: 1px solid var(--line-strong);
  border-radius: 8px;
  padding: 0 8px 0 12px;
  height: 40px;
  min-width: 0;
  flex: 0 1 320px;
  transition:
    border-color 0.15s,
    box-shadow 0.15s,
    background 0.15s;
}
.search-form:focus-within {
  border-color: var(--green);
  box-shadow: var(--ring);
  background: var(--white);
}
.search-form > span {
  display: grid;
  place-items: center;
}
.search-form > span svg {
  width: 17px;
  height: 17px;
}
.search-form input {
  min-width: 0;
  width: 100%;
  flex: 1;
  border: none;
  background: none;
  font-size: 14px;
  color: var(--ink);
  padding: 5px 2px;
  outline: none;
}
.search-form input:focus-visible {
  outline: none;
}
.search-form kbd {
  border: 1px solid var(--line-strong);
  border-bottom-width: 2px;
  border-radius: 5px;
  background: var(--white);
  color: var(--muted);
  font-size: 11px;
  padding: 1px 7px;
}
#main {
  padding: 36px 40px 48px;
  width: 100%;
  max-width: 1440px;
  margin: 0 auto;
  outline: none;
  position: relative;
  flex: 1;
}

/* ---------------------------------------------------------------------------
   Shared controls
   --------------------------------------------------------------------------- */
.btn {
  border: 1px solid var(--line-strong);
  background: var(--white);
  color: var(--ink);
  border-radius: var(--radius-sm);
  padding: 9px 16px;
  font-size: 14px;
  line-height: 1.4;
  display: inline-flex;
  gap: 10px;
  justify-content: center;
  align-items: center;
  font-weight: 500;
  min-height: 40px;
  box-shadow: var(--shadow-sm);
  transition:
    background 0.15s,
    border-color 0.15s,
    transform 0.15s,
    box-shadow 0.15s;
}
.btn:hover {
  background: var(--surface-raised);
  border-color: var(--subtle);
}
.btn:active {
  transform: translateY(1px);
}
.btn-primary {
  background: var(--green);
  color: var(--on-accent);
  border-color: var(--green);
  box-shadow:
    0 1px 2px rgba(15, 23, 42, 0.12),
    0 6px 16px -6px color-mix(in srgb, var(--green) 70%, transparent);
}
.btn-primary:hover {
  background: var(--primary-strong);
  border-color: var(--primary-strong);
}
.btn-secondary {
  background: var(--surface-raised);
}
.btn-secondary:hover {
  background: var(--surface-hover);
}
.btn-acid {
  background: var(--acid);
  border-color: var(--acid);
  color: #052e1f;
}
.btn-acid:hover {
  background: color-mix(in srgb, var(--acid) 85%, white);
  border-color: color-mix(in srgb, var(--acid) 85%, white);
}
.btn-quiet {
  background: transparent;
  border-color: transparent;
  box-shadow: none;
  padding-left: 0;
  padding-right: 0;
}
.btn-quiet:hover {
  background: transparent;
  border-color: transparent;
  color: var(--green);
}
.text-link {
  font-size: 14px;
  font-weight: 500;
  color: var(--green);
  text-decoration: underline;
  text-decoration-color: color-mix(in srgb, var(--green) 35%, transparent);
  text-underline-offset: 4px;
  transition: text-decoration-color 0.15s;
}
.text-link:hover {
  text-decoration-color: currentColor;
}
.pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 1px solid var(--line);
  background: var(--surface-raised);
  color: var(--muted);
  padding: 3px 10px;
  font: 500 11px var(--mono);
  border-radius: 999px;
  white-space: nowrap;
}
.tag {
  font: 11px var(--mono);
  color: var(--muted);
}
.muted {
  color: var(--muted);
}
.card {
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.overline {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font: 500 11px var(--mono);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 22px;
  padding: 6px 12px 6px 10px;
  border-radius: 999px;
  border: 1px solid color-mix(in srgb, var(--green) 25%, var(--line));
  background: color-mix(in srgb, var(--white) 75%, transparent);
  color: var(--green);
}
.overline:before {
  content: '';
  width: 7px;
  height: 7px;
  border-radius: 2px;
  background: var(--green);
  transform: rotate(45deg);
}
.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin-top: 28px;
}
.hero-actions .btn {
  min-height: 44px;
  padding-inline: 20px;
  font-size: 15px;
}
.section-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 20px;
}
.section-head h2 {
  font-size: 28px;
}
.section-head .eyebrow {
  margin-bottom: 8px;
  display: block;
}
.section-rule {
  padding-top: 8px;
}
.path-table {
  align-self: start;
  border: 1px solid var(--line);
  background: var(--white);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}
.path-row {
  display: grid;
  grid-template-columns: 44px 1fr auto;
  gap: 14px;
  align-items: center;
  padding: 16px 20px;
  border-bottom: 1px solid var(--line);
  position: relative;
  transition: background 0.15s;
}
.path-row:last-child {
  border-bottom: none;
}
.path-row:hover {
  background: var(--surface-raised);
}
.path-row:hover .arrow {
  color: var(--green);
  transform: translate(2px, -2px);
}
.path-number {
  font: 600 13px var(--mono);
  color: var(--muted);
  border: 1px solid var(--line-strong);
  background: var(--white);
  height: 36px;
  width: 36px;
  display: grid;
  place-items: center;
  border-radius: 9px;
}
.path-row.is-current .path-number,
.path-row:first-child .path-number {
  background: var(--primary-soft);
  border-color: color-mix(in srgb, var(--green) 35%, transparent);
  color: var(--green);
}
.path-row.is-complete .path-number {
  background: var(--emerald-soft);
  border-color: color-mix(in srgb, var(--acid) 40%, transparent);
  color: var(--emerald-ink);
}
.path-row h3 {
  font-size: 17px;
}
.path-row p {
  font-size: 13px;
  color: var(--muted);
  margin-top: 3px;
}
.path-row-end {
  font: 500 12px var(--mono);
  color: var(--muted);
  text-align: right;
  display: flex;
  gap: 18px;
  align-items: center;
}
.path-row-end .arrow {
  font-size: 18px;
  transition:
    transform 0.15s,
    color 0.15s;
}
.progress-rail {
  width: 56px;
  height: 6px;
  background: var(--surface-hover);
  border-radius: 999px;
  display: block;
  margin-top: 7px;
  overflow: hidden;
}
.progress-rail i {
  display: block;
  background: var(--acid);
  height: 100%;
  border-radius: inherit;
}
.experiment-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(210px, 1fr));
  gap: 16px;
}
.experiment-card {
  padding: 20px;
  border: 1px solid var(--line);
  background: var(--white);
  display: flex;
  flex-direction: column;
  min-height: 210px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  overflow-wrap: break-word;
  transition:
    transform 0.2s,
    box-shadow 0.2s,
    border-color 0.2s;
}
.experiment-card:hover {
  border-color: color-mix(in srgb, var(--green) 40%, var(--line));
  box-shadow: var(--shadow-md);
  transform: translateY(-3px);
}
.experiment-card h2 {
  font-size: 18px;
  letter-spacing: -0.015em;
  margin: 12px 0 8px;
}
.experiment-card p {
  font-size: 13px;
  color: var(--muted);
}
.experiment-card .mini-graphic {
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  color: var(--green);
  font-family: var(--mono);
  font-size: 16px;
  white-space: nowrap;
  overflow: hidden;
  padding: 10px 12px;
  margin-top: 14px;
  border-radius: var(--radius-sm);
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
  background-size: 10px 10px;
  border: 1px solid var(--line);
}
.mini-graphic i {
  height: 18px;
  width: 11px;
  border-radius: 3px;
  background: var(--green);
  display: block;
}
.mini-graphic i:nth-child(even) {
  background: var(--acid);
  height: 30px;
}
/* Dashboard: the card for beginners, shown until the learning path is in use. */
.dash-beginner {
  padding: 28px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--white);
  box-shadow: var(--shadow-sm);
}
.dash-beginner h2 {
  margin: 6px 0 8px;
  font-size: 24px;
  letter-spacing: -0.015em;
}
.dash-beginner p {
  max-width: 62ch;
  color: var(--muted);
}
.dash-beginner .hero-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px 20px;
  margin-top: 18px;
}

/* Labs catalog (#/labs): filters, the experiment and workbench cards, Python challenges. */
.lab-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px 20px;
  margin-bottom: 20px;
}
.lab-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.lab-filters a {
  padding: 6px 14px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--white);
  color: var(--muted);
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
}
.lab-filters a:hover {
  border-color: var(--line-strong);
  color: var(--ink);
}
.lab-filters a[aria-current='page'] {
  background: var(--primary-soft);
  border-color: color-mix(in srgb, var(--green) 45%, var(--line));
  color: var(--ink);
  font-weight: 600;
}
.lab-count {
  font: 500 12px var(--mono);
  color: var(--muted);
}
.lab-cards {
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
}
.lab-card.is-bench {
  border-top: 3px solid var(--acid);
}
.lab-card.is-experiment {
  border-top: 3px solid var(--green);
}
.lab-group {
  margin-top: 32px;
}
.lab-group-head {
  margin-bottom: 14px;
}
.lab-group-head h2 {
  font-size: 22px;
  letter-spacing: -0.015em;
}
.lab-group-head p {
  color: var(--muted);
  font-size: 14px;
}
.lab-challenges {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 12px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.lab-challenges a {
  display: flex;
  flex-direction: column;
  gap: 4px;
  height: 100%;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-left: 3px solid var(--orange);
  border-radius: var(--radius);
  background: var(--white);
  color: inherit;
  text-decoration: none;
  transition:
    border-color 0.2s,
    box-shadow 0.2s;
}
.lab-challenges a:hover {
  border-color: var(--line-strong);
  box-shadow: var(--shadow-sm);
}
.lab-challenges a.is-solved {
  border-left-color: var(--acid);
}
.lab-challenges strong {
  font-size: 16px;
}
.lab-challenges span {
  font-size: 13px;
  color: var(--muted);
}
.lab-challenges .lab-challenge-level {
  font: 600 11px var(--mono);
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--subtle);
}
.lab-challenges .lab-challenge-state {
  margin-top: auto;
  padding-top: 6px;
  font: 500 11px var(--mono);
  color: var(--green);
}
.lab-challenges a.is-solved .lab-challenge-state {
  color: var(--emerald-ink);
}
.experiment-card .card-bottom {
  font: 500 11px var(--mono);
  color: var(--green);
  margin-top: auto;
  padding-top: 16px;
  display: flex;
  justify-content: space-between;
}
.footer {
  font: 11px var(--mono);
  color: var(--subtle);
  padding: 20px 40px;
  border-top: 1px solid var(--line);
  background: color-mix(in srgb, var(--white) 70%, transparent);
  display: flex;
  justify-content: space-between;
  gap: 15px;
  letter-spacing: 0.03em;
  position: relative;
}
.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 20px;
}
.footer a:hover {
  color: var(--green);
}
.footer-slash {
  margin: 0 12px;
  color: var(--line-strong);
}

/* Portal home: a personal dashboard */
.dash-hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(320px, 0.9fr);
  gap: 32px;
  align-items: center;
  padding: 12px 0 28px;
}
.dash-hero h1 {
  font-size: clamp(34px, 3.6vw, 48px);
  margin: 10px 0 12px;
}
.dash-hero .eyebrow {
  color: var(--muted);
}
.dash-hero p {
  font-size: 17px;
  color: var(--lede);
  margin-bottom: 18px;
}
.dash-next {
  display: grid;
  gap: 8px;
  padding: 24px;
  background: var(--white);
  border: 1px solid color-mix(in srgb, var(--green) 30%, var(--line));
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  transition:
    transform 0.2s,
    box-shadow 0.2s;
}
.dash-next:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}
.dash-next .eyebrow {
  color: var(--green);
}
.dash-next strong {
  font-size: 22px;
  letter-spacing: -0.02em;
}
.dash-next-summary {
  font-size: 15px;
  color: var(--muted);
}
.dash-next .btn {
  justify-self: start;
  margin-top: 8px;
}
.dash-stats {
  list-style: none;
  padding: 0;
  margin: 0 0 28px;
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}
.dash-stats.is-three {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}
.dash-stats li {
  display: grid;
  gap: 2px;
  padding: 16px 18px;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.dash-stats strong {
  font: 600 28px var(--mono);
  color: var(--ink);
}
.dash-stats strong small {
  font-size: 15px;
  color: var(--subtle);
}
.dash-stats span {
  font-size: 13px;
  color: var(--muted);
}
.dash-stats .text-link {
  font-size: 13px;
  margin-top: 4px;
}
.dash-section {
  margin-bottom: 36px;
}
.dash-section .stage-cards {
  margin-top: 0;
}
.dash-quick {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
  margin-top: 12px;
}
.dash-quick a {
  display: grid;
  gap: 4px;
  padding: 18px;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  transition:
    border-color 0.15s,
    transform 0.2s;
}
.dash-quick a:hover {
  border-color: color-mix(in srgb, var(--green) 40%, var(--line));
  transform: translateY(-2px);
}
.dash-quick .nav-symbol {
  color: var(--green);
  margin-bottom: 6px;
}
.dash-quick strong {
  font-size: 16px;
}
.dash-quick small {
  font-size: 13px;
  color: var(--muted);
}
.dash-about {
  display: inline-block;
  margin-top: 18px;
  font-size: 13px;
}

/* ---------------------------------------------------------------------------
   Page headings, toolbars, and the learning path
   --------------------------------------------------------------------------- */
.page-heading {
  margin: 4px 0 32px;
}
.page-heading h1 {
  font-size: clamp(34px, 3.6vw, 48px);
  margin: 12px 0;
}
.page-heading .eyebrow {
  color: var(--muted);
}
.page-heading p {
  font-size: 16px;
  color: var(--lede);
  max-width: 680px;
}
.page-toolbar {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 22px;
}
.page-toolbar input,
.page-toolbar select {
  border: 1px solid var(--line-strong);
  background-color: var(--white);
  border-radius: 8px;
  padding: 9px 13px;
  min-height: 42px;
  font-size: 14px;
  color: var(--ink);
  box-shadow: var(--shadow-sm);
}
.page-toolbar input:focus-visible,
.page-toolbar select:focus-visible {
  outline: none;
  border-color: var(--green);
  box-shadow: var(--ring);
}
.page-toolbar select {
  max-width: 100%;
  min-width: 0;
}
.page-toolbar input {
  min-width: 220px;
  flex: 1;
}
.track-section {
  padding: 28px 0 18px;
  scroll-margin-top: 90px;
}
.track-section + .track-section {
  border-top: 1px solid var(--line);
}
.track-header {
  display: flex;
  gap: 18px;
  margin-bottom: 20px;
}
.track-header .path-number {
  flex: none;
  background: var(--primary-soft);
  border-color: color-mix(in srgb, var(--green) 35%, transparent);
  color: var(--green);
  width: 46px;
  height: 46px;
  border-radius: 12px;
  font-size: 15px;
}
.track-header h2 {
  font-size: 28px;
  margin-top: 4px;
}
.track-header p {
  font-size: 15px;
  color: var(--muted);
  margin-top: 8px;
}
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 16px;
}
.lesson-card {
  border: 1px solid var(--line);
  padding: 20px;
  background: var(--white);
  min-height: 180px;
  display: flex;
  flex-direction: column;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  position: relative;
  transition:
    transform 0.2s,
    box-shadow 0.2s,
    border-color 0.2s;
}
.lesson-card:hover {
  border-color: color-mix(in srgb, var(--green) 40%, var(--line));
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}
.lesson-card.done {
  border-color: color-mix(in srgb, var(--acid) 45%, var(--line));
  background: linear-gradient(180deg, var(--emerald-soft), var(--white) 70%);
}
.lesson-card.done .eyebrow {
  color: var(--emerald-ink);
}
.lesson-card h3 {
  font-size: 18px;
  margin: 12px 0 8px;
}
.lesson-card p {
  font-size: 14px;
  color: var(--muted);
  margin-bottom: 16px;
}
.lesson-card footer {
  font: 500 11px var(--mono);
  color: var(--green);
  margin-top: auto;
  display: flex;
  justify-content: space-between;
  gap: 10px;
}

/* ---------------------------------------------------------------------------
   Lessons: a calm reading surface with no decoration
   --------------------------------------------------------------------------- */
.lesson-page {
  max-width: 1080px;
  margin-inline: auto;
}
.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, 740px) 250px;
  gap: 48px;
  align-items: start;
}
.lesson-content h1 {
  font-size: clamp(34px, 3.4vw, 46px);
  margin: 14px 0 20px;
}
.lesson-content .intro {
  font-size: 18px;
  line-height: 1.75;
  color: var(--muted);
  margin-bottom: 25px;
}
.objectives {
  background: var(--primary-soft);
  border: 1px solid color-mix(in srgb, var(--green) 20%, transparent);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 25px 0;
}
.objectives h2 {
  font: 600 11px var(--mono);
  letter-spacing: 0.07em;
  color: var(--green);
  margin-bottom: 10px;
}
.objectives ul {
  margin: 0;
  padding-left: 18px;
  font-size: 15px;
  line-height: 1.85;
}
.lesson-section {
  margin: 36px 0;
}
.lesson-section h2 {
  font-size: 26px;
  margin-bottom: 14px;
}
.lesson-section p {
  font-size: 16px;
  line-height: 1.85;
  white-space: pre-line;
  max-width: 68ch;
}
.lesson-aside {
  position: sticky;
  top: 92px;
  font-size: 13px;
}
.lesson-aside h3 {
  font: 600 11px var(--mono);
  letter-spacing: 0.07em;
  color: var(--subtle);
  margin-bottom: 10px;
}
.lesson-aside .side-item {
  display: block;
  padding: 8px 12px;
  margin: 2px 0;
  border-radius: var(--radius-sm);
  color: var(--muted);
  transition: background 0.15s;
}
.lesson-aside .side-item:hover {
  background: var(--surface-raised);
  color: var(--ink);
}
.lesson-aside .side-item.active {
  color: var(--green);
  background: var(--primary-soft);
  font-weight: 600;
}
.lesson-aside textarea {
  width: 100%;
  min-height: 175px;
  background: var(--white);
  border: 1px solid var(--line-strong);
  color: var(--ink);
  padding: 12px;
  font-size: 14px;
  resize: vertical;
  border-radius: var(--radius);
  line-height: 1.6;
  margin-top: 10px;
}
.lesson-aside textarea:focus-visible {
  outline: none;
  border-color: var(--green);
  box-shadow: var(--ring);
}
.aside-notes {
  margin-top: 25px;
}
.aside-notes label {
  font: 600 11px var(--mono);
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--subtle);
}
.callout {
  border: 1px solid var(--line);
  background: var(--white);
  padding: 20px 24px;
  margin: 25px 0;
  border-radius: var(--radius);
}
.callout h2,
.callout h3 {
  font: 600 12px var(--mono);
  margin-bottom: 9px;
  letter-spacing: 0.04em;
}
.callout p {
  font-size: 15px;
  line-height: 1.75;
}
.callout.warning {
  border-color: color-mix(in srgb, var(--orange) 35%, transparent);
  border-left: 4px solid var(--orange);
  background: var(--warning-surface);
}
.callout.warning h3 {
  color: var(--warning-ink);
}
.checkpoint {
  background: var(--white);
  border: 1px solid var(--line);
  padding: 28px;
  margin-top: 30px;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}
.checkpoint h2 {
  font-size: 26px;
  margin: 12px 0 18px;
}
.quiz-part {
  border: 0;
  margin: 0 0 26px;
  padding: 0;
  min-width: 0;
}
.quiz-part legend {
  padding: 0;
}
/* The legend holds the question, so screen readers announce it with the options. */
.quiz-part legend .eyebrow,
.quiz-part legend .quiz-question {
  display: block;
}
.quiz-part legend .eyebrow {
  margin-bottom: 8px;
}
.quiz-part .feedback {
  margin-top: 12px;
}
.quiz-question {
  font-size: 17px;
  font-weight: 500;
  line-height: 1.6;
  margin-bottom: 15px;
}
.quiz-options {
  display: grid;
  gap: 8px;
  margin-bottom: 18px;
}
.quiz-option {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 13px 14px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  font-size: 15px;
  cursor: pointer;
  background: var(--white);
  transition:
    border-color 0.15s,
    background 0.15s;
}
.quiz-option:hover {
  border-color: color-mix(in srgb, var(--green) 45%, var(--line-strong));
}
.quiz-option:has(input:checked) {
  border-color: var(--green);
  background: var(--primary-soft);
  box-shadow: 0 0 0 1px var(--green);
}
.quiz-option input {
  margin-top: 4px;
  accent-color: var(--green);
}
.feedback {
  font-size: 15px;
  line-height: 1.7;
  padding: 14px 16px;
  margin: 16px 0;
  background: var(--emerald-soft);
  border: 1px solid color-mix(in srgb, var(--acid) 35%, transparent);
  border-left: 4px solid var(--acid);
  border-radius: var(--radius-sm);
}
.feedback.wrong {
  background: var(--warning-surface);
  border-color: color-mix(in srgb, var(--orange) 35%, transparent);
  border-left-color: var(--orange);
}
.feedback-explanation {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid color-mix(in srgb, var(--orange) 35%, transparent);
}
.feedback-explanation:focus {
  outline: none;
}
.feedback-reveal {
  margin-top: 8px;
  padding: 0;
  border: 0;
  background: none;
  font-family: inherit;
  cursor: pointer;
}
.lesson-next {
  margin: 30px 0;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 15px;
}
.resources {
  font-size: 14px;
  margin-top: 20px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}
.resources a {
  display: block;
  color: var(--green);
  text-decoration: underline;
  text-decoration-color: color-mix(in srgb, var(--green) 35%, transparent);
  text-underline-offset: 3px;
  margin: 7px 0;
}
.back-link {
  font: 500 12px var(--mono);
  display: inline-flex;
  margin-bottom: 22px;
  color: var(--muted);
}
.back-link:hover {
  color: var(--green);
}
.empty-state {
  padding: 52px 24px;
  border: 1px dashed var(--line-strong);
  border-radius: var(--radius-lg);
  background: color-mix(in srgb, var(--white) 70%, transparent);
  text-align: center;
  color: var(--muted);
}
.empty-state p {
  margin-inline: auto;
}
.empty-state h2 {
  margin-bottom: 10px;
  color: var(--ink);
}
.notice {
  font-size: 14px;
  padding: 14px 18px;
  background: var(--primary-soft);
  border: 1px solid color-mix(in srgb, var(--green) 20%, transparent);
  margin: 22px 0;
  border-radius: var(--radius);
}

/* ---------------------------------------------------------------------------
   Projects, notebook, glossary, diagnostic, and search
   --------------------------------------------------------------------------- */
.project-hero {
  display: grid;
  grid-template-columns: 1.3fr 1fr;
  gap: 28px;
  margin: 25px 0 35px;
}
.project-brief {
  padding: 30px;
  background: var(--panel-green);
  color: var(--panel-ink);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
  isolation: isolate;
}
.project-brief:before {
  content: '';
  position: absolute;
  inset: 0;
  z-index: -1;
  background:
    radial-gradient(circle at 100% 0%, rgba(37, 99, 235, 0.4), transparent 50%),
    linear-gradient(rgba(148, 163, 184, 0.07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(148, 163, 184, 0.07) 1px, transparent 1px);
  background-size:
    auto,
    20px 20px,
    20px 20px;
}
.project-brief h2 {
  font-size: 30px;
  margin: 15px 0;
  color: #fff;
}
.project-brief p {
  font-size: 15px;
  color: var(--panel-muted);
  line-height: 1.8;
}
.project-brief .eyebrow {
  color: #93c5fd;
}
.project-brief ul {
  font-size: 14px;
  padding-left: 17px;
  line-height: 2;
}
.project-brief .btn:not(.btn-primary):not(.btn-acid) {
  background: rgba(255, 255, 255, 0.06);
  border-color: rgba(148, 163, 184, 0.35);
  color: #fff;
}
.project-brief .btn:not(.btn-primary):not(.btn-acid):hover {
  background: rgba(255, 255, 255, 0.12);
}
.project-brief .text-link {
  color: #93c5fd;
}
.milestone {
  display: grid;
  grid-template-columns: 50px 1fr;
  gap: 18px;
  padding: 24px;
  margin: 14px 0;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.milestone h2 {
  font-size: 24px;
  margin-bottom: 8px;
}
.milestone p {
  font-size: 15px;
  color: var(--muted);
  line-height: 1.75;
}
.milestone details {
  margin-top: 18px;
}
.milestone summary {
  cursor: pointer;
  font: 600 12px var(--mono);
  color: var(--green);
}
.milestone li {
  font-size: 15px;
  margin: 10px 0;
  line-height: 1.7;
}
.check-row {
  display: flex;
  gap: 10px;
  align-items: center;
  margin-top: 15px;
  font-size: 14px;
}
.check-row input {
  accent-color: var(--acid);
  width: 18px;
  height: 18px;
}
.notebook-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  margin: 27px 0;
}
.notebook-stat {
  padding: 22px;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.notebook-stat strong {
  display: block;
  font: 600 36px var(--mono);
  color: var(--green);
  margin-bottom: 4px;
}
.notebook-stat span {
  font: 11px var(--mono);
  color: var(--muted);
}
.notebook-note {
  margin: 14px 0;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  padding: 22px;
}
.notebook-note h3 {
  font-size: 19px;
  margin-bottom: 12px;
}
.notebook-note p {
  font-size: 15px;
  line-height: 1.75;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}
.glossary {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px 16px;
}
.glossary-item {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--white);
  padding: 16px 18px;
}
.glossary-item h3 {
  font-size: 17px;
  margin-bottom: 6px;
}
.glossary-item p {
  font-size: 14px;
  color: var(--muted);
  line-height: 1.7;
}
.glossary-item .text-link {
  display: block;
  margin-top: 10px;
  font-size: 13px;
}
.diagnostic-result {
  padding: 28px;
  background: var(--panel-green);
  color: var(--panel-ink);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  margin: 25px 0;
}
.diagnostic-result .eyebrow {
  color: #93c5fd;
}
.diagnostic-result h2 {
  margin: 12px 0;
  color: #fff;
}
.diagnostic-result p {
  margin: 10px 0 20px;
  font-size: 15px;
  color: var(--panel-muted);
}
.toast {
  position: fixed;
  bottom: 25px;
  left: calc(50% + var(--sidebar-width) / 2);
  transform: translate(-50%, 8px);
  background: var(--ink);
  color: var(--paper);
  padding: 12px 20px;
  z-index: 50;
  opacity: 0;
  pointer-events: none;
  transition:
    opacity 0.18s,
    transform 0.18s;
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  font-size: 14px;
  max-width: 90vw;
}
.toast.show {
  opacity: 1;
  transform: translate(-50%, 0);
}
/* Another tab saved with a newer version: saving pauses here until a reload. */
.update-notice {
  position: fixed;
  left: calc(var(--sidebar-width) + 24px);
  bottom: 24px;
  z-index: 40;
  display: flex;
  align-items: center;
  gap: 16px;
  max-width: min(480px, calc(100vw - var(--sidebar-width) - 48px));
  padding: 12px 12px 12px 16px;
  background: var(--white);
  color: var(--ink);
  border: 1px solid color-mix(in srgb, var(--orange) 40%, var(--line));
  border-left: 4px solid var(--orange);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  font-size: 14px;
  line-height: 1.5;
}
.update-notice .btn {
  flex: none;
}
.search-result {
  display: block;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--white);
  padding: 20px 22px;
  margin: 12px 0;
  transition:
    border-color 0.15s,
    box-shadow 0.15s;
}
.search-result:hover {
  border-color: color-mix(in srgb, var(--green) 40%, var(--line));
  box-shadow: var(--shadow-md);
}
.search-result h2 {
  font-size: 22px;
  letter-spacing: -0.015em;
  margin: 8px 0;
}
.search-result p {
  font-size: 14px;
  color: var(--muted);
}
.search-result:hover h3 {
  color: var(--green);
}

/* Architecture and retrieval practice share the laboratory's work surfaces. */
.wide-textarea {
  display: block;
  width: 100%;
  min-height: 190px;
  padding: 16px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--white);
  color: var(--ink);
  font-size: 15px;
  line-height: 1.7;
  resize: vertical;
  margin: 12px 0 18px;
}
.wide-textarea:focus-visible {
  outline: none;
  border-color: var(--green);
  box-shadow: var(--ring);
}
.architecture-diagram {
  display: flex;
  align-items: center;
  gap: 13px;
  margin-top: 26px;
  flex-wrap: wrap;
}
.architecture-diagram div {
  border: 1px solid rgba(147, 197, 253, 0.45);
  background: rgba(37, 99, 235, 0.16);
  border-radius: var(--radius-sm);
  padding: 13px;
  font: 12px var(--mono);
  color: #dbeafe;
  flex: 1;
  text-align: center;
}
.architecture-diagram > span {
  color: #34d399;
}
.recall-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 15px;
  flex-wrap: wrap;
}
/* A region that may scroll sideways (a wide diagram or table on a phone): reachable by
   keyboard (tabindex="0", role="region", a name), and shaded at an edge while more
   content lies beyond it. The covers move with the content, the shadows stay put. */
.scroll-region {
  --scroll-cover: var(--white);
  --scroll-shade: color-mix(in srgb, var(--ink) 30%, transparent);
  overflow-x: auto;
  background:
    linear-gradient(to right, var(--scroll-cover) 30%, transparent) left / 28px 100% no-repeat local,
    linear-gradient(to left, var(--scroll-cover) 30%, transparent) right / 28px 100% no-repeat local,
    radial-gradient(farthest-side at 0 50%, var(--scroll-shade), transparent) left / 14px 100%
      no-repeat scroll,
    radial-gradient(farthest-side at 100% 50%, var(--scroll-shade), transparent) right / 14px 100%
      no-repeat scroll;
}
.scroll-region:focus-visible {
  outline: 2px solid var(--green);
  outline-offset: 2px;
}
.evidence-table-wrap {
  overflow-x: auto;
  margin: 30px 0;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background-color: var(--white);
}
.evidence-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  line-height: 1.7;
  min-width: 570px;
}
.evidence-table td,
.evidence-table th {
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--line);
  padding: 16px;
}
.evidence-table tr:last-child td {
  border-bottom: 0;
}
.evidence-table th {
  font: 600 11px var(--mono);
  color: var(--muted);
  background: var(--surface-raised);
}
.evidence-table td:first-child {
  font-weight: 600;
  width: 20%;
}
.evidence-table td:nth-child(2) {
  width: 35%;
}
.architecture-desk {
  max-width: 1000px;
}
.architecture-desk .project-brief p {
  max-width: 75ch;
}

/* A second project carries the same laboratory language into AI-assisted work. */
.ai-entry {
  display: grid;
  grid-template-columns: minmax(0, 1.6fr) minmax(220px, 1fr);
  gap: 40px;
  padding: 34px;
  margin-top: 56px;
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.ai-entry h2 {
  font-size: clamp(27px, 3vw, 36px);
  line-height: 1.12;
  margin: 12px 0 15px;
}
.ai-entry p {
  color: var(--muted);
  font-size: 16px;
  line-height: 1.7;
  max-width: 530px;
}
.ai-entry .hero-actions {
  flex-wrap: wrap;
  gap: 18px;
}
.ai-loop {
  list-style: none;
  align-self: center;
  padding: 0;
  margin: 0;
  counter-reset: loop;
}
.ai-loop li {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 0;
  border-bottom: 1px dashed var(--line-strong);
  font-size: 15px;
  font-weight: 500;
}
.ai-loop li:last-child {
  border-bottom: 0;
}
.ai-loop span {
  font: 600 11px var(--mono);
  color: var(--green);
  background: var(--primary-soft);
  border-radius: 6px;
  padding: 3px 7px;
}
.project-switcher {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px;
  margin-bottom: 34px;
  padding: 6px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--surface-raised);
}
.project-switcher a {
  padding: 14px 18px;
  display: grid;
  gap: 6px;
  min-width: 0;
  border-radius: var(--radius);
  transition: background 0.15s;
}
.project-switcher a[aria-current] {
  background: var(--white);
  box-shadow: var(--shadow-md);
}
.project-switcher a[aria-current] strong {
  color: var(--green);
}
.project-switcher a:hover:not([aria-current]) {
  background: color-mix(in srgb, var(--white) 55%, transparent);
}
.project-switcher strong {
  font-size: 16px;
  font-weight: 600;
}
/* Learning paths: the chosen path is raised; paths still to come are shown, muted. */
.path-switcher {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
  gap: 6px;
  margin-bottom: 18px;
  padding: 6px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--surface-raised);
}
.path-switcher > * {
  display: grid;
  align-content: start;
  gap: 6px;
  min-width: 0;
  padding: 14px 18px;
  border-radius: var(--radius);
}
.path-switcher a {
  transition: background 0.15s;
}
.path-switcher a[aria-current] {
  background: var(--white);
  box-shadow: var(--shadow-md);
}
.path-switcher a[aria-current] strong {
  color: var(--green);
}
.path-switcher a:hover:not([aria-current]) {
  background: color-mix(in srgb, var(--white) 55%, transparent);
}
.path-switcher strong {
  font-size: 16px;
  font-weight: 600;
}
.path-switcher .is-coming strong {
  color: var(--muted);
  font-weight: 500;
}
.path-summary {
  max-width: 760px;
  margin-bottom: 24px;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.7;
}
.path-summary strong {
  color: var(--ink);
}
.dash-section .path-switcher {
  margin-bottom: 16px;
}
.dash-path {
  display: grid;
  gap: 4px;
  margin-bottom: 14px;
}
.dash-path strong {
  font-size: 18px;
  font-weight: 600;
  letter-spacing: -0.015em;
}
.track-project-link {
  margin: 0 0 22px 64px;
  font-size: 14px;
}
.ai-status {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  margin: 20px 0 26px;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--white);
  font-size: 15px;
  line-height: 1.7;
}

/* Backup panel: export, import with a preview, and the backup reminder. */
.backup-panel {
  margin: 20px 0 34px;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--white);
  box-shadow: var(--shadow-sm);
  /* Clears the sticky top bar when the sidebar link scrolls here. */
  scroll-margin-top: 88px;
}
.backup-panel:focus {
  outline: none;
}
.backup-panel h2 {
  font-size: 24px;
  margin: 8px 0 10px;
}
.backup-panel > p {
  max-width: 700px;
  margin-bottom: 18px;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.7;
}
.backup-panel > .page-toolbar {
  margin-bottom: 12px;
}
.backup-panel > .backup-when {
  margin: 0;
  font: 11px/1.6 var(--mono);
  color: var(--subtle);
}
.backup-panel > .backup-note {
  margin: 16px 0 0;
  font-size: 12px;
  color: var(--muted);
}
.backup-reminder {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin: 0 0 18px;
  padding: 14px 18px;
}
.backup-reminder p {
  font-size: 14px;
  line-height: 1.6;
}
.backup-reminder .btn {
  flex: none;
}
.storage-badge.is-due span {
  background: var(--orange);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--orange) 22%, transparent);
}
.import-preview {
  margin-top: 20px;
  padding: 20px;
  border: 1px solid color-mix(in srgb, var(--green) 25%, transparent);
  border-radius: var(--radius);
  background: var(--primary-soft);
}
.import-preview:focus {
  outline: none;
}
.import-preview h3 {
  font-size: 17px;
  margin-bottom: 8px;
  overflow-wrap: anywhere;
}
.import-preview h3 code {
  font: 500 13px var(--mono);
}
.import-preview > p {
  font-size: 14px;
  line-height: 1.6;
}
.import-preview fieldset {
  display: grid;
  gap: 12px;
  margin: 16px 0 18px;
  padding: 0;
  border: 0;
  min-width: 0;
}
.import-choice {
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--white);
  font-size: 14px;
  line-height: 1.6;
}
.import-choice:has(input:checked) {
  border-color: var(--green);
  box-shadow: 0 0 0 1px var(--green);
}
.import-choice label {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  cursor: pointer;
}
.import-choice input {
  flex: none;
  margin: 5px 0 0;
  accent-color: var(--green);
}
.import-choice p,
.import-choice ul,
.import-choice details {
  margin: 6px 0 0 23px;
  color: var(--muted);
}
.import-choice ul {
  padding-left: 18px;
}
.import-choice li {
  overflow-wrap: anywhere;
}
.import-choice details ul {
  margin-left: 0;
}
.import-choice .import-kept {
  color: var(--warning-ink);
}
.import-choice summary {
  cursor: pointer;
  color: var(--ink);
}
.import-preview .page-toolbar {
  margin-bottom: 0;
}

/* ---------------------------------------------------------------------------
   Find your starting point: one step at a time
   --------------------------------------------------------------------------- */
.dx-root {
  max-width: 1180px;
}
.dx-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 24px;
  align-items: start;
}
.dx-main {
  min-width: 0;
}
.dx-side {
  position: sticky;
  top: 92px;
  display: grid;
  gap: 16px;
}
.dx-side-card {
  padding: 20px;
  box-shadow: var(--shadow-sm);
}
.dx-how ol {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 10px;
}
.dx-how li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 14px;
  line-height: 1.5;
}
.dx-how li span {
  flex: none;
  display: grid;
  place-items: center;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--primary-soft);
  color: var(--green);
  font: 600 12px var(--mono);
}
.dx-how .dx-hint {
  margin-top: 14px;
  font-size: 13px;
}
.dx-card {
  background: var(--white);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  padding: 28px;
}
.dx-fieldset {
  border: 0;
  padding: 0;
  margin: 0 0 26px;
  min-width: 0;
}
.dx-fieldset legend,
.dx-card h2 {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1.4;
  margin-bottom: 14px;
  outline: none;
}
.dx-fieldset legend .muted {
  font-size: 14px;
  font-weight: 400;
}
.dx-choices {
  display: grid;
  gap: 10px;
}
.dx-choices-4 {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}
.dx-choices-chips {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}
.dx-choice {
  position: relative;
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 14px;
  border: 1.5px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--white);
  cursor: pointer;
  transition:
    border-color 0.15s,
    background 0.15s,
    box-shadow 0.15s;
}
.dx-choices-4 .dx-choice {
  flex-direction: column;
}
.dx-choice:hover {
  border-color: color-mix(in srgb, var(--green) 45%, var(--line-strong));
}
.dx-choice input,
.dx-option input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}
.dx-choice:has(input:focus-visible),
.dx-option:has(input:focus-visible) {
  outline: 2px solid var(--green);
  outline-offset: 2px;
}
.dx-choice.is-selected,
.dx-choice:has(input:checked) {
  border-color: var(--green);
  background: var(--primary-soft);
  box-shadow: 0 0 0 1px var(--green);
}
.dx-choice-icon {
  flex: none;
  display: grid;
  place-items: center;
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: var(--surface-raised);
  color: var(--green);
}
.dx-choice-icon:empty {
  display: none;
}
.dx-choice-icon svg {
  width: 20px;
  height: 20px;
}
.dx-choice strong {
  display: block;
  font-size: 15px;
  font-weight: 600;
}
.dx-choice small {
  display: block;
  margin-top: 2px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.45;
}
.dx-choices-chips .dx-choice {
  align-items: center;
  padding: 11px 14px;
}
.dx-choices-chips .dx-choice strong {
  font-size: 14px;
  font-weight: 500;
}
.dx-callout {
  margin-top: 4px;
  padding: 18px 20px;
  border-radius: var(--radius);
  background: var(--emerald-soft);
  border: 1px solid color-mix(in srgb, var(--acid) 40%, transparent);
}
.dx-callout strong {
  font-size: 17px;
}
.dx-callout p {
  margin-top: 6px;
  color: var(--muted);
  font-size: 15px;
}
.dx-actions {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px;
  margin-top: 20px;
}
.dx-actions .btn-quiet {
  margin-right: auto;
}
.dx-hint {
  margin-top: 14px;
  font-size: 14px;
  color: var(--muted);
}
.dx-progress {
  height: 6px;
  border-radius: 999px;
  background: var(--surface-hover);
  overflow: hidden;
}
.dx-progress i {
  display: block;
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--green), var(--acid));
  transition: width 0.3s ease;
}
.dx-count {
  margin: 10px 0 14px;
  font: 600 11px var(--mono);
  letter-spacing: 0.06em;
  color: var(--subtle);
}
.dx-stage {
  display: inline-block;
  margin-bottom: 10px;
  padding: 3px 10px;
  border-radius: 999px;
  background: var(--primary-soft);
  color: var(--green);
  font: 500 12px var(--sans);
}
.dx-options {
  display: grid;
  gap: 8px;
}
.dx-option {
  position: relative;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  border: 1.5px solid var(--line-strong);
  border-radius: var(--radius);
  font-size: 15px;
  line-height: 1.5;
  cursor: pointer;
  transition:
    border-color 0.15s,
    background 0.15s;
}
.dx-option:hover {
  border-color: color-mix(in srgb, var(--green) 45%, var(--line-strong));
}
.dx-option.is-selected,
.dx-option:has(input:checked) {
  border-color: var(--green);
  background: var(--primary-soft);
}
.dx-option.is-unsure {
  border-style: dashed;
  color: var(--muted);
}
.dx-option.is-right {
  border-color: var(--acid);
  background: var(--emerald-soft);
}
.dx-option.is-wrong {
  border-color: var(--orange);
  background: var(--warning-surface);
}
.dx-option.is-answer {
  border-color: var(--acid);
  border-style: dashed;
}
.dx-option:has(input:disabled) {
  cursor: default;
}
.dx-letter {
  flex: none;
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 8px;
  background: var(--surface-raised);
  border: 1px solid var(--line-strong);
  font: 600 12px var(--mono);
  color: var(--muted);
}
.dx-option:has(input:checked) .dx-letter {
  background: var(--green);
  border-color: var(--green);
  color: var(--on-accent);
}
.dx-result {
  display: grid;
  gap: 18px;
}
.dx-result .diagnostic-result {
  margin: 0;
}
.dx-result .diagnostic-result h2 {
  outline: none;
}
.dx-meta {
  font: 500 12px var(--mono);
  color: #93c5fd !important;
  margin: 0 !important;
}
.dx-card .dx-map-title {
  font: 600 11px var(--mono);
  letter-spacing: 0.07em;
  color: var(--subtle);
  margin-bottom: 12px;
}
.dx-map {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 6px;
}
.dx-map-item {
  display: grid;
  grid-template-columns: 34px 1fr auto;
  align-items: center;
  gap: 12px;
  padding: 8px 10px;
  border-radius: var(--radius-sm);
}
.dx-map-item a:hover {
  color: var(--green);
}
.dx-map-num {
  display: grid;
  place-items: center;
  height: 26px;
  border-radius: 7px;
  border: 1px solid var(--line-strong);
  font: 600 11px var(--mono);
  color: var(--muted);
}
.dx-map-status {
  font: 500 12px var(--sans);
  padding: 2px 9px;
  border-radius: 999px;
  color: var(--muted);
  background: var(--surface-raised);
}
.dx-map-item.is-familiar .dx-map-status,
.dx-map-item.is-familiar .dx-map-num {
  color: var(--emerald-ink);
  background: var(--emerald-soft);
  border-color: color-mix(in srgb, var(--acid) 40%, transparent);
}
.dx-map-item.is-learn .dx-map-status,
.dx-map-item.is-learn .dx-map-num {
  color: var(--warning-ink);
  background: var(--warning-surface);
  border-color: color-mix(in srgb, var(--orange) 40%, transparent);
}
.dx-map-item.is-current {
  background: var(--primary-soft);
  font-weight: 600;
}
.dx-map-item.is-current .dx-map-num,
.dx-map-item.is-current .dx-map-status {
  background: var(--green);
  border-color: var(--green);
  color: var(--on-accent);
}
.dx-map-item.is-upcoming {
  color: var(--muted);
}
.dx-side .dx-map-item {
  grid-template-columns: 30px 1fr auto;
  gap: 10px;
  padding: 7px 8px;
  font-size: 14px;
}
.dx-side .dx-map-status {
  font-size: 11px;
}
.dx-map-item.is-start {
  background: var(--primary-soft);
}
.dx-map-item.is-start .dx-map-num,
.dx-map-item.is-start .dx-map-status {
  background: var(--green);
  border-color: var(--green);
  color: var(--on-accent);
}
@media (max-width: 1100px) {
  .dx-layout {
    grid-template-columns: 1fr;
  }
  .dx-side {
    position: static;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  }
}
@media (max-width: 900px) {
  .dx-choices-4 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .dx-choices-chips {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}
@media (max-width: 650px) {
  .dx-card {
    padding: 20px 16px;
  }
  .dx-choices-chips,
  .dx-choices-4 {
    grid-template-columns: 1fr;
  }
  .dx-choices-4 .dx-choice {
    flex-direction: row;
    align-items: center;
  }
}

/* ---------------------------------------------------------------------------
   Collapsible navigation rail
   --------------------------------------------------------------------------- */
.sidebar,
.workspace {
  transition:
    width 0.22s ease,
    margin-left 0.22s ease,
    padding 0.22s ease;
}
.sidebar-toggle {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 12px;
  padding: 8px 12px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  background: none;
  color: var(--subtle);
  font-size: 13px;
  font-weight: 500;
  text-align: left;
}
.sidebar-toggle:hover {
  background: var(--surface-raised);
  color: var(--ink);
}
.sidebar-toggle svg {
  width: 19px;
  height: 19px;
  flex: none;
}
@media (min-width: 651px) {
  html[data-sidebar='collapsed'] {
    --sidebar-width: 72px;
  }
  html[data-sidebar='collapsed'] .sidebar {
    padding-inline: 12px;
    overflow: visible;
  }
  html[data-sidebar='collapsed'] .brand {
    justify-content: center;
    padding-inline: 0;
  }
  html[data-sidebar='collapsed'] .brand > span:last-child,
  html[data-sidebar='collapsed'] .nav-label,
  html[data-sidebar='collapsed'] .sidebar-toggle span {
    position: absolute;
    width: 1px;
    height: 1px;
    overflow: hidden;
    clip: rect(0 0 0 0);
    white-space: nowrap;
  }
  html[data-sidebar='collapsed'] .sidebar-caption {
    visibility: hidden;
    height: 0;
    margin-bottom: 0;
  }
  html[data-sidebar='collapsed'] .sidebar-bottom {
    display: none;
  }
  html[data-sidebar='collapsed'] #navigation {
    margin-top: 14px;
  }
  html[data-sidebar='collapsed'] .nav-link,
  html[data-sidebar='collapsed'] .sidebar-toggle {
    justify-content: center;
    padding: 10px 0;
    position: relative;
  }
  html[data-sidebar='collapsed'] .sidebar-toggle {
    margin-top: auto;
  }
  html[data-sidebar='collapsed'] .sidebar-toggle-chevron {
    transform: translateX(-1.5px) scaleX(-1);
    transform-origin: 14.5px 12px;
  }
  /* Names appear beside the icons on hover and keyboard focus. */
  html[data-sidebar='collapsed'] .nav-link:after {
    content: attr(data-label);
    position: absolute;
    left: calc(100% + 12px);
    top: 50%;
    transform: translate(-4px, -50%);
    padding: 6px 10px;
    border-radius: var(--radius-sm);
    background: var(--ink);
    color: var(--paper);
    font-size: 13px;
    font-weight: 500;
    white-space: nowrap;
    box-shadow: var(--shadow-md);
    opacity: 0;
    pointer-events: none;
    transition:
      opacity 0.15s,
      transform 0.15s;
  }
  html[data-sidebar='collapsed'] .nav-link:hover:after,
  html[data-sidebar='collapsed'] .nav-link:focus-visible:after {
    opacity: 1;
    transform: translate(0, -50%);
  }
}

/* ---------------------------------------------------------------------------
   Responsive layout
   --------------------------------------------------------------------------- */
@media (max-width: 1180px) {
  :root {
    --sidebar-width: 208px;
  }
  .sidebar {
    padding-inline: 10px;
  }
  .brand {
    font-size: 14px;
  }
  .topbar {
    padding-inline: 24px;
    gap: 14px;
  }
  #main {
    padding: 30px 26px 40px;
  }
  .lesson-grid {
    grid-template-columns: 1fr 1fr;
  }
  .lesson-layout {
    grid-template-columns: minmax(0, 1fr) 210px;
    gap: 28px;
  }
}
@media (max-width: 900px) {
  :root {
    --sidebar-width: 184px;
  }
  .dash-hero {
    grid-template-columns: 1fr;
  }
  .dash-stats,
  .dash-stats.is-three,
  .dash-quick {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
  .brand {
    font-size: 13px;
    gap: 8px;
  }
  .brand-mark {
    width: 28px;
    height: 28px;
  }
  .brand-caption {
    font-size: 10px;
    letter-spacing: 0;
  }
  .nav-link {
    font-size: 13.5px;
    padding: 8px 10px;
    gap: 9px;
  }
  .sidebar-bottom {
    padding: 13px;
  }
  .lesson-layout {
    grid-template-columns: 1fr;
  }
  .lesson-aside {
    position: static;
    border-top: 1px solid var(--line);
    padding-top: 25px;
  }
  .lesson-aside .side-item,
  .lesson-aside > h3 {
    display: none;
  }
  .aside-notes {
    margin-top: 0;
  }
  .project-hero {
    grid-template-columns: 1fr;
  }
  .breadcrumb {
    font-size: 11px;
  }
  .footer {
    padding-inline: 26px;
  }
  .footer a {
    display: none;
  }
  .notebook-stats {
    grid-template-columns: 1fr 1fr;
  }
}
@media (max-width: 650px) {
  :root {
    --sidebar-width: 0px;
    --phone-bar: 60px;
  }
  body {
    padding-bottom: calc(var(--phone-bar) + env(safe-area-inset-bottom));
  }

  /* The navigation becomes a sheet that rises from the bottom bar. */
  .sidebar {
    inset: auto 0 0 0;
    width: auto;
    max-height: min(84vh, 640px);
    padding: 0 16px calc(env(safe-area-inset-bottom) + 18px);
    border-right: 0;
    border-top: 1px solid var(--line);
    border-radius: 18px 18px 0 0;
    box-shadow: var(--shadow-lg);
    z-index: 50;
    transform: translateY(100%);
    visibility: hidden;
    transition:
      transform 0.26s ease,
      visibility 0s linear 0.26s;
  }
  html.menu-open .sidebar {
    transform: none;
    visibility: visible;
    transition: transform 0.26s ease;
  }
  /* While the sheet is open the page behind stays put. */
  html.menu-open,
  html.menu-open body {
    overflow: hidden;
  }
  .sidebar {
    overscroll-behavior: contain;
  }
  .phone-scrim {
    touch-action: none;
  }
  .sidebar .brand,
  .sidebar-toggle {
    display: none;
  }
  .sheet-head {
    position: sticky;
    top: 0;
    z-index: 1;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 0 12px;
    background: var(--white);
  }
  .sheet-handle {
    display: block;
    position: absolute;
    top: 8px;
    left: 50%;
    width: 40px;
    height: 4px;
    border-radius: 2px;
    background: var(--line-strong);
    transform: translateX(-50%);
  }
  .sidebar-caption {
    margin: 0 2px;
  }
  .sheet-close {
    display: inline-grid;
    place-items: center;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    border: 1px solid var(--line);
    background: var(--surface-raised);
    color: var(--muted);
  }
  .sheet-close svg {
    width: 18px;
    height: 18px;
  }
  #navigation {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 8px;
  }
  .nav-link {
    min-height: 54px;
    margin: 0;
    padding: 10px 12px;
    border-color: var(--line);
    border-radius: var(--radius);
    font-size: 14px;
    line-height: 1.2;
  }
  .sheet-settings {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-top: 16px;
    padding: 14px 2px;
    border-block: 1px solid var(--line);
  }
  .sidebar-bottom {
    margin-top: 14px;
    padding: 12px 14px;
  }

  /* The bar itself: menu, current section, search. */
  .phone-bar {
    position: fixed;
    inset: auto 0 0 0;
    z-index: 35;
    display: grid;
    grid-template-columns: auto minmax(0, 1fr) auto;
    align-items: center;
    gap: 10px;
    height: calc(var(--phone-bar) + env(safe-area-inset-bottom));
    padding: 0 12px env(safe-area-inset-bottom);
    border-top: 1px solid var(--line);
    background: color-mix(in srgb, var(--white) 90%, transparent);
    backdrop-filter: blur(14px) saturate(1.4);
    -webkit-backdrop-filter: blur(14px) saturate(1.4);
  }
  .phone-bar-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    height: 42px;
    padding: 0 16px 0 13px;
    border: 1px solid var(--line);
    border-radius: 999px;
    background: var(--surface-raised);
    color: var(--ink);
    font: 600 14px var(--sans);
  }
  .phone-bar-button svg {
    width: 20px;
    height: 20px;
    flex: none;
  }
  .phone-bar-search {
    width: 42px;
    padding: 0;
  }
  .phone-bar-button[aria-expanded='true'] {
    background: var(--primary-soft);
    border-color: color-mix(in srgb, var(--green) 30%, transparent);
    color: var(--green);
  }
  .phone-current {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    min-width: 0;
    font: 500 11px var(--mono);
    letter-spacing: 0.05em;
    color: var(--muted);
  }
  .phone-current > span:last-child {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
  }
  .phone-current .nav-symbol {
    color: var(--green);
  }
  .phone-current .nav-symbol:empty {
    display: none;
  }
  .phone-current .nav-symbol svg {
    width: 18px;
    height: 18px;
  }
  .phone-scrim {
    display: block;
    position: fixed;
    inset: 0;
    z-index: 44;
    background: rgb(15 23 42 / 0.4);
  }
  .toast {
    bottom: calc(var(--phone-bar) + env(safe-area-inset-bottom) + 14px);
  }
  .update-notice {
    left: 12px;
    right: 12px;
    bottom: calc(var(--phone-bar) + env(safe-area-inset-bottom) + 12px);
    max-width: none;
  }
  .workspace {
    margin-left: 0;
  }
  .search-form kbd {
    display: none;
  }
  .breadcrumb span {
    padding-inline: 7px;
  }
  #main {
    padding: 24px 16px 36px;
    min-height: 65vh;
  }
  .overline {
    font-size: 10px;
    margin-bottom: 18px;
  }
  .section-head {
    align-items: start;
    flex-direction: column;
    gap: 10px;
  }
  .section-head h2 {
    font-size: 24px;
  }
  .path-row {
    padding: 14px;
    gap: 10px;
    grid-template-columns: 34px 1fr auto;
  }
  .path-number {
    width: 32px;
    height: 32px;
    font-size: 12px;
  }
  .path-row h3 {
    font-size: 15px;
  }
  .path-row p {
    font-size: 12px;
  }
  .path-row-end {
    gap: 10px;
    font-size: 11px;
  }
  .experiment-cards {
    grid-template-columns: 1fr;
  }
  .page-heading h1 {
    font-size: 34px;
  }
  .page-heading p {
    font-size: 15px;
  }
  .lesson-grid {
    grid-template-columns: 1fr;
  }
  .lesson-card {
    min-height: 150px;
  }
  .track-header {
    gap: 14px;
  }
  .track-header h2 {
    font-size: 24px;
  }
  .track-project-link {
    margin-left: 0;
  }
  .lesson-content h1 {
    font-size: 34px;
  }
  .lesson-content .intro {
    font-size: 16px;
  }
  .lesson-section p {
    font-size: 15px;
  }
  .checkpoint {
    padding: 20px;
  }
  .notebook-stat {
    padding: 18px;
  }
  .glossary {
    grid-template-columns: 1fr;
  }
  .footer {
    padding: 18px 16px;
    font-size: 10px;
    flex-wrap: wrap;
  }
  .footer a {
    display: block;
  }
  .footer-slash {
    margin: 0 6px;
  }
  .toast {
    width: max-content;
  }
  .page-toolbar input {
    min-width: 180px;
  }
  .milestone {
    grid-template-columns: 1fr;
    gap: 10px;
    padding: 20px;
  }
  .project-brief {
    padding: 24px;
  }
  .project-brief .btn {
    flex-wrap: wrap;
  }
  .architecture-diagram {
    display: grid;
    grid-template-columns: 1fr;
    gap: 5px;
  }
  .architecture-diagram > span {
    text-align: center;
    transform: rotate(90deg);
  }
  .wide-textarea {
    font-size: 16px;
  }
  .recall-top .pill {
    white-space: normal;
  }
  .ai-entry {
    grid-template-columns: minmax(0, 1fr);
    gap: 24px;
    padding: 24px;
  }
  .project-switcher a,
  .path-switcher > * {
    padding: 12px;
  }
  .path-switcher {
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  }
  .path-switcher .eyebrow {
    font-size: 10px;
    line-height: 1.5;
  }
  .path-switcher strong {
    font-size: 14px;
  }
  .project-switcher .eyebrow {
    font-size: 10px;
    line-height: 1.5;
  }
  .project-switcher strong {
    font-size: 14px;
  }
  .ai-status,
  .backup-reminder {
    align-items: start;
    flex-direction: column;
    gap: 12px;
  }
  .backup-panel {
    padding: 18px;
    scroll-margin-top: 16px;
  }
  .import-preview {
    padding: 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  *,
  *:before,
  *:after {
    scroll-behavior: auto !important;
    transition: none !important;
    animation: none !important;
  }
}