:root {
  color-scheme: light;
  --app-bg: #e8ecef;
  --surface: #fbfcfd;
  --surface-raised: #ffffff;
  --surface-soft: #f1f4f5;
  --surface-strong: #24282e;
  --ink: #181b1f;
  --ink-soft: #5e6872;
  --ink-faint: #87919a;
  --line: #d7dde1;
  --line-strong: #bcc5cb;
  --sidebar: #171a1f;
  --sidebar-hover: #24282e;
  --sidebar-active: #30353b;
  --sidebar-ink: #f6f7f8;
  --sidebar-muted: #aeb6bf;
  --coral: #d25f45;
  --coral-soft: #f7e7e2;
  --teal: #167e77;
  --teal-soft: #dff0ed;
  --amber: #bf8120;
  --amber-soft: #f6ecd5;
  --blue: #2b65ad;
  --blue-soft: #e3ebf6;
  --green: #367a57;
  --green-soft: #e1eee7;
  --violet: #7755a4;
  --violet-soft: #ece6f4;
  --danger: #b64343;
  --shadow: 0 18px 45px rgba(25, 31, 36, 0.12);
  --topbar-height: 64px;
  --sidebar-width: 286px;
  --controlbar-height: 70px;
  --radius: 6px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  font-family: "Microsoft YaHei", "PingFang SC", "Noto Sans CJK SC", Arial, sans-serif;
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --app-bg: #16191c;
  --surface: #202428;
  --surface-raised: #272c31;
  --surface-soft: #2d3237;
  --surface-strong: #101214;
  --ink: #f1f3f4;
  --ink-soft: #bac2c9;
  --ink-faint: #8f9aa3;
  --line: #3a4147;
  --line-strong: #525b63;
  --sidebar: #0f1113;
  --sidebar-hover: #1e2226;
  --sidebar-active: #2b3035;
  --coral: #ed7b61;
  --coral-soft: #452b27;
  --teal: #55bdb2;
  --teal-soft: #203d3a;
  --amber: #e3ad4a;
  --amber-soft: #423722;
  --blue: #78a8e4;
  --blue-soft: #26384e;
  --green: #72bd91;
  --green-soft: #263e31;
  --violet: #af8bd8;
  --violet-soft: #372d44;
  --danger: #ef7b7b;
  --shadow: 0 18px 45px rgba(0, 0, 0, 0.32);
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
  margin: 0;
}

body {
  min-width: 320px;
  overflow: hidden;
  background: var(--app-bg);
  color: var(--ink);
}

button,
select,
input {
  font: inherit;
}

button,
a,
select,
input[type="range"] {
  -webkit-tap-highlight-color: transparent;
}

button:focus-visible,
a:focus-visible,
select:focus-visible,
input:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--blue) 45%, transparent);
  outline-offset: 2px;
}

button {
  color: inherit;
}

.app-shell {
  display: grid;
  grid-template-rows: var(--topbar-height) minmax(0, 1fr);
  height: 100dvh;
}

.topbar {
  position: relative;
  z-index: 40;
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr) auto;
  align-items: center;
  min-height: var(--topbar-height);
  background: var(--surface-raised);
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  align-self: stretch;
  padding: 0 22px;
  background: var(--sidebar);
  color: var(--sidebar-ink);
  text-decoration: none;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 32px;
  height: 32px;
  border: 1px solid rgba(255, 255, 255, 0.28);
  border-radius: 50%;
  color: #f6b89f;
  font-family: Georgia, serif;
  font-size: 20px;
}

.brand-copy {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.brand-copy strong {
  font-size: 15px;
  font-weight: 700;
}

.brand-copy small {
  margin-top: 2px;
  color: var(--sidebar-muted);
  font-size: 11px;
}

.current-context {
  display: flex;
  align-items: center;
  min-width: 0;
  padding: 0 24px;
  overflow: hidden;
}

.phase-label {
  flex: 0 0 auto;
  color: var(--coral);
  font-size: 12px;
  font-weight: 700;
}

.context-divider {
  width: 1px;
  height: 18px;
  margin: 0 14px;
  background: var(--line);
}

.current-lesson {
  min-width: 0;
  overflow: hidden;
  color: var(--ink-soft);
  font-size: 13px;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.top-actions {
  display: flex;
  align-items: center;
  gap: 4px;
  padding-right: 14px;
}

.icon-button,
.nav-button {
  position: relative;
  display: inline-grid;
  place-items: center;
  width: 40px;
  height: 40px;
  padding: 0;
  border: 1px solid transparent;
  border-radius: var(--radius);
  background: transparent;
  cursor: pointer;
}

.icon-button:hover,
.nav-button:hover {
  background: var(--surface-soft);
  border-color: var(--line);
}

.icon-button svg,
.nav-button svg,
.reveal-button svg,
.action-button svg,
.media-zoom svg {
  width: 18px;
  height: 18px;
  stroke-width: 1.8;
}

[data-tooltip]::after {
  position: absolute;
  z-index: 120;
  right: 0;
  bottom: -34px;
  width: max-content;
  max-width: 180px;
  padding: 6px 8px;
  border-radius: 4px;
  background: var(--surface-strong);
  color: #f8f9fa;
  content: attr(data-tooltip);
  font-size: 11px;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-4px);
  transition: opacity 150ms ease, transform 150ms ease;
}

[data-tooltip]:hover::after,
[data-tooltip]:focus-visible::after {
  opacity: 1;
  transform: translateY(0);
}

.workspace {
  position: relative;
  display: grid;
  grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  min-height: 0;
}

.sidebar {
  position: relative;
  z-index: 30;
  display: flex;
  min-height: 0;
  flex-direction: column;
  background: var(--sidebar);
  color: var(--sidebar-ink);
}

.sidebar-progress {
  padding: 20px 22px 18px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.09);
}

.progress-copy {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
  color: var(--sidebar-muted);
  font-size: 11px;
}

.progress-copy strong {
  color: var(--sidebar-ink);
  font-variant-numeric: tabular-nums;
  font-weight: 600;
}

.progress-track {
  height: 3px;
  overflow: hidden;
  background: rgba(255, 255, 255, 0.13);
}

.progress-track span {
  display: block;
  width: 0;
  height: 100%;
  background: var(--coral);
  transition: width 420ms var(--ease);
}

.course-nav {
  flex: 1;
  min-height: 0;
  padding: 16px 12px 20px;
  overflow-y: auto;
  scrollbar-color: rgba(255, 255, 255, 0.2) transparent;
  scrollbar-width: thin;
}

.nav-phase + .nav-phase {
  margin-top: 20px;
}

.nav-phase-title {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 10px 8px;
  color: var(--sidebar-muted);
  font-size: 10px;
  font-weight: 700;
}

.nav-phase-title::before {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--phase-color, var(--coral));
  content: "";
}

.lesson-link {
  display: grid;
  grid-template-columns: 30px minmax(0, 1fr) auto;
  align-items: center;
  width: 100%;
  min-height: 42px;
  padding: 7px 10px;
  border: 0;
  border-left: 2px solid transparent;
  border-radius: 3px;
  background: transparent;
  color: var(--sidebar-muted);
  cursor: pointer;
  text-align: left;
}

.lesson-link:hover {
  background: var(--sidebar-hover);
  color: var(--sidebar-ink);
}

.lesson-link.is-active {
  border-left-color: var(--phase-color, var(--coral));
  background: var(--sidebar-active);
  color: var(--sidebar-ink);
}

.lesson-number {
  color: var(--phase-color, var(--coral));
  font-size: 11px;
  font-variant-numeric: tabular-nums;
  font-weight: 700;
}

.lesson-link-label {
  min-width: 0;
  overflow: hidden;
  font-size: 12px;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.lesson-page-count {
  color: #7d8790;
  font-size: 10px;
  font-variant-numeric: tabular-nums;
}

.sidebar-footer {
  display: grid;
  gap: 8px;
  padding: 14px 22px 18px;
  border-top: 1px solid rgba(255, 255, 255, 0.09);
}

.keyboard-hint {
  display: flex;
  align-items: center;
  gap: 5px;
  color: #7f8992;
  font-size: 10px;
}

kbd {
  min-width: 22px;
  padding: 2px 5px;
  border: 1px solid rgba(255, 255, 255, 0.18);
  border-radius: 3px;
  color: var(--sidebar-muted);
  font-family: inherit;
  font-size: 9px;
  text-align: center;
}

.presentation {
  display: grid;
  grid-template-rows: minmax(0, 1fr) var(--controlbar-height);
  min-width: 0;
  min-height: 0;
}

.stage-wrap {
  display: grid;
  min-height: 0;
  place-items: center;
  padding: 24px 30px;
  overflow: hidden;
}

.slide-surface {
  position: relative;
  width: min(100%, 1260px);
  max-height: 100%;
  min-height: min(690px, 100%);
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
  scrollbar-color: var(--line-strong) transparent;
  scrollbar-width: thin;
}

.slide-surface::before {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  background: var(--slide-color, var(--coral));
  content: "";
}

.slide-loading {
  display: grid;
  min-height: 520px;
  place-content: center;
  color: var(--ink-soft);
  text-align: center;
}

.loading-note {
  color: var(--coral);
  font-family: Georgia, serif;
  font-size: 36px;
}

.slide-inner {
  display: flex;
  min-height: 100%;
  flex-direction: column;
  padding: 42px 48px 38px;
}

.slide-header {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 24px;
  align-items: start;
  margin-bottom: 26px;
}

.slide-kicker,
.drawer-kicker {
  display: block;
  margin-bottom: 8px;
  color: var(--slide-color, var(--coral));
  font-size: 11px;
  font-weight: 800;
}

.slide-title {
  max-width: 900px;
  margin: 0;
  color: var(--ink);
  font-family: "STSong", "SimSun", Georgia, serif;
  font-size: 36px;
  font-weight: 700;
  line-height: 1.22;
}

.slide-lead {
  max-width: 920px;
  margin: 12px 0 0;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.85;
}

.source-page {
  min-width: 42px;
  padding-top: 5px;
  color: var(--ink-faint);
  font-size: 11px;
  font-variant-numeric: tabular-nums;
  text-align: right;
}

.slide-body {
  display: flex;
  flex: 1;
  min-height: 0;
  flex-direction: column;
}

.slide-body.split-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(360px, 0.92fr);
  gap: 42px;
  align-items: center;
}

.hero-slide {
  position: relative;
  display: grid;
  min-height: 620px;
  padding: 54px 58px;
  overflow: hidden;
  background:
    linear-gradient(90deg, color-mix(in srgb, var(--surface) 97%, transparent), color-mix(in srgb, var(--surface) 78%, transparent)),
    repeating-linear-gradient(0deg, transparent 0 26px, color-mix(in srgb, var(--line) 38%, transparent) 26px 27px);
}

.hero-slide::after {
  position: absolute;
  right: -70px;
  bottom: -90px;
  width: 340px;
  height: 340px;
  border: 1px solid color-mix(in srgb, var(--slide-color, var(--coral)) 30%, transparent);
  border-radius: 50%;
  content: "";
}

.hero-content {
  position: relative;
  z-index: 1;
  display: flex;
  max-width: 900px;
  flex-direction: column;
  justify-content: center;
}

.hero-index {
  margin-bottom: 24px;
  color: var(--slide-color, var(--coral));
  font-size: 13px;
  font-weight: 800;
}

.hero-title {
  margin: 0;
  color: var(--ink);
  font-family: "STSong", "SimSun", Georgia, serif;
  font-size: 58px;
  font-weight: 700;
  line-height: 1.18;
}

.hero-subtitle {
  max-width: 760px;
  margin: 22px 0 0;
  color: var(--ink-soft);
  font-size: 17px;
  line-height: 1.8;
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 14px 28px;
  margin-top: 42px;
  padding-top: 22px;
  border-top: 1px solid var(--line);
  color: var(--ink-soft);
  font-size: 12px;
}

.hero-meta span {
  display: inline-flex;
  align-items: center;
  gap: 8px;
}

.hero-meta span::before {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--slide-color, var(--coral));
  content: "";
}

.content-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px 32px;
  align-content: start;
}

.content-grid.cols-3 {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.content-grid.cols-4 {
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
}

.concept-block {
  position: relative;
  min-width: 0;
  padding: 18px 0 6px;
  border-top: 2px solid var(--block-color, var(--line-strong));
}

.concept-index {
  display: block;
  margin-bottom: 8px;
  color: var(--block-color, var(--slide-color, var(--coral)));
  font-size: 11px;
  font-weight: 800;
}

.concept-block h3 {
  margin: 0 0 8px;
  color: var(--ink);
  font-size: 16px;
  font-weight: 700;
  line-height: 1.45;
}

.concept-block p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 13px;
  line-height: 1.75;
}

.formula-band {
  display: flex;
  align-items: center;
  gap: 22px;
  margin: 6px 0 28px;
  padding: 17px 20px;
  border-left: 4px solid var(--slide-color, var(--coral));
  background: var(--surface-soft);
}

.formula-label {
  flex: 0 0 auto;
  color: var(--slide-color, var(--coral));
  font-size: 11px;
  font-weight: 800;
}

.formula-value {
  color: var(--ink);
  font-family: Georgia, "Times New Roman", serif;
  font-size: 22px;
  font-weight: 700;
}

.callout-line {
  margin-top: auto;
  padding: 14px 0 0 18px;
  border-left: 3px solid var(--amber);
  color: var(--ink-soft);
  font-size: 13px;
  line-height: 1.75;
}

.media-frame {
  position: relative;
  display: grid;
  min-width: 0;
  place-items: center;
  padding: 18px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: #ffffff;
}

.media-frame img {
  display: block;
  width: 100%;
  max-height: 430px;
  object-fit: contain;
}

.media-zoom {
  position: absolute;
  right: 10px;
  bottom: 10px;
  display: inline-grid;
  place-items: center;
  width: 38px;
  height: 38px;
  padding: 0;
  border: 1px solid #d7dde1;
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.94);
  color: #30363b;
  cursor: pointer;
}

.media-caption {
  margin: 10px 0 0;
  color: var(--ink-faint);
  font-size: 11px;
  line-height: 1.6;
}

.practice-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 18px;
}

.practice-step {
  min-width: 0;
  padding: 18px 0 0;
  border-top: 3px solid var(--step-color, var(--coral));
}

.practice-icon {
  display: grid;
  width: 34px;
  height: 34px;
  margin-bottom: 13px;
  place-items: center;
  border-radius: 50%;
  background: var(--step-soft, var(--coral-soft));
  color: var(--step-color, var(--coral));
  font-size: 12px;
  font-weight: 800;
}

.practice-step h3 {
  margin: 0 0 7px;
  font-size: 15px;
}

.practice-step p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 12px;
  line-height: 1.7;
}

.standards {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 20px;
  margin-top: 30px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}

.standard-item {
  display: grid;
  grid-template-columns: 30px minmax(0, 1fr);
  gap: 12px;
}

.standard-check {
  display: grid;
  width: 28px;
  height: 28px;
  place-items: center;
  border-radius: 50%;
  background: var(--green-soft);
  color: var(--green);
  font-weight: 800;
}

.standard-item strong {
  display: block;
  margin-bottom: 5px;
  font-size: 13px;
}

.standard-item p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 12px;
  line-height: 1.65;
}

.controlbar {
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr) auto 44px;
  gap: 14px;
  align-items: center;
  min-width: 0;
  padding: 10px 22px;
  border-top: 1px solid var(--line);
  background: var(--surface-raised);
}

.nav-button {
  width: 44px;
  height: 44px;
  border-color: var(--line);
  background: var(--surface);
}

.nav-button-primary {
  border-color: var(--ink);
  background: var(--ink);
  color: var(--surface);
}

.nav-button-primary:hover {
  border-color: var(--ink);
  background: color-mix(in srgb, var(--ink) 88%, var(--surface));
}

.nav-button:disabled {
  opacity: 0.36;
  cursor: not-allowed;
}

.page-context {
  display: flex;
  min-width: 0;
  flex-direction: column;
}

.page-context span,
.page-context strong {
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.page-context span {
  margin-bottom: 3px;
  color: var(--ink-faint);
  font-size: 10px;
}

.page-context strong {
  color: var(--ink);
  font-size: 12px;
  font-weight: 700;
}

.reveal-button,
.action-button,
.segmented button,
.choice-button {
  display: inline-flex;
  min-height: 38px;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 8px 13px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  cursor: pointer;
  font-size: 12px;
  font-weight: 700;
}

.reveal-button:hover,
.action-button:hover,
.segmented button:hover,
.choice-button:hover {
  border-color: var(--ink-soft);
  background: var(--surface-soft);
}

.reveal-button.is-complete {
  color: var(--green);
}

.action-button.primary {
  border-color: var(--ink);
  background: var(--ink);
  color: var(--surface);
}

.action-button.ghost {
  border-color: transparent;
  background: transparent;
  color: var(--ink-soft);
}

.action-button svg {
  flex: 0 0 auto;
}

.mobile-only {
  display: none;
}

.sidebar-scrim,
.drawer-scrim {
  position: fixed;
  z-index: 24;
  display: none;
  inset: var(--topbar-height) 0 0;
  padding: 0;
  border: 0;
  background: rgba(7, 9, 11, 0.5);
}

.notes-drawer {
  position: fixed;
  z-index: 80;
  top: 0;
  right: 0;
  display: flex;
  width: min(400px, 92vw);
  height: 100dvh;
  flex-direction: column;
  border-left: 1px solid var(--line);
  background: var(--surface-raised);
  box-shadow: -16px 0 40px rgba(10, 14, 18, 0.18);
  transform: translateX(102%);
  transition: transform 280ms var(--ease);
}

.notes-drawer.is-open {
  transform: translateX(0);
}

.drawer-scrim {
  z-index: 70;
  inset: 0;
}

.drawer-scrim.is-visible {
  display: block;
}

.drawer-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  padding: 26px 24px 20px;
  border-bottom: 1px solid var(--line);
}

.drawer-header h2 {
  margin: 0;
  font-size: 20px;
}

.drawer-content {
  flex: 1;
  padding: 24px;
  overflow-y: auto;
}

.drawer-content p {
  margin: 0 0 18px;
  color: var(--ink-soft);
  font-size: 13px;
  line-height: 1.8;
}

.teacher-prompt {
  padding: 14px 0 14px 18px;
  border-left: 3px solid var(--amber);
}

.teacher-prompt strong {
  display: block;
  margin-bottom: 6px;
  color: var(--ink);
  font-size: 12px;
}

.media-dialog {
  width: min(1180px, calc(100vw - 48px));
  max-width: none;
  max-height: calc(100dvh - 48px);
  padding: 46px 24px 18px;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-raised);
  color: var(--ink);
  box-shadow: var(--shadow);
}

.media-dialog::backdrop {
  background: rgba(7, 9, 11, 0.72);
}

.media-dialog img {
  display: block;
  width: 100%;
  max-height: calc(100dvh - 150px);
  object-fit: contain;
  background: #fff;
}

.media-dialog p {
  margin: 12px 0 0;
  color: var(--ink-soft);
  font-size: 12px;
  text-align: center;
}

.dialog-close {
  position: absolute;
  top: 8px;
  right: 8px;
}

.toast {
  position: fixed;
  z-index: 150;
  right: 20px;
  bottom: 88px;
  max-width: min(360px, calc(100vw - 40px));
  padding: 11px 14px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--surface-strong);
  color: #f7f8f9;
  box-shadow: var(--shadow);
  font-size: 12px;
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity 180ms ease, transform 180ms ease;
}

.toast.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* Interactive teaching tools */
.lab-area {
  display: flex;
  min-height: 0;
  flex: 1;
  flex-direction: column;
}

.lab-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: end;
  gap: 12px;
  padding: 14px 0 18px;
  border-top: 1px solid var(--line);
}

.field {
  display: grid;
  gap: 6px;
}

.field label,
.range-field label {
  color: var(--ink-soft);
  font-size: 10px;
  font-weight: 700;
}

.field select {
  min-width: 112px;
  height: 38px;
  padding: 0 34px 0 10px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--surface-raised);
  color: var(--ink);
  cursor: pointer;
}

.segmented {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 4px;
}

.segmented button {
  min-height: 36px;
  padding: 7px 11px;
}

.segmented button[aria-pressed="true"],
.choice-button[aria-pressed="true"] {
  border-color: var(--ink);
  background: var(--ink);
  color: var(--surface);
}

.lab-stage {
  display: grid;
  grid-template-columns: minmax(0, 1.45fr) minmax(220px, 0.55fr);
  gap: 24px;
  align-items: center;
  min-height: 0;
  flex: 1;
  padding: 20px 0 0;
  border-top: 1px solid var(--line);
}

.lab-stage.stacked {
  grid-template-columns: minmax(0, 1fr);
}

.lab-readout {
  align-self: stretch;
  padding: 18px 0 18px 22px;
  border-left: 1px solid var(--line);
}

.readout-label {
  display: block;
  margin-bottom: 7px;
  color: var(--ink-faint);
  font-size: 10px;
  font-weight: 800;
}

.readout-value {
  display: block;
  margin-bottom: 7px;
  color: var(--ink);
  font-family: "STSong", "SimSun", Georgia, serif;
  font-size: 30px;
  font-weight: 700;
  line-height: 1.25;
}

.readout-detail {
  color: var(--ink-soft);
  font-size: 12px;
  line-height: 1.7;
}

.tone-token-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 16px;
}

.tone-token {
  display: inline-grid;
  min-width: 34px;
  height: 34px;
  padding: 0 8px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--surface-soft);
  color: var(--ink);
  font-size: 11px;
  font-weight: 700;
}

.tone-token.is-root {
  border-color: var(--coral);
  background: var(--coral-soft);
  color: var(--coral);
}

.staff-visual {
  position: relative;
  width: 100%;
  min-height: 190px;
  overflow: hidden;
  border: 1px solid var(--line);
  background: #fff;
}

.staff-lines {
  position: absolute;
  top: 52px;
  right: 26px;
  left: 48px;
  height: 88px;
  background: repeating-linear-gradient(to bottom, #c6cbd0 0 1px, transparent 1px 21px);
  border-right: 1px solid #c6cbd0;
  border-left: 1px solid #c6cbd0;
}

.clef-symbol {
  position: absolute;
  z-index: 2;
  top: 42px;
  left: 54px;
  color: #171a1f;
  font-family: "Segoe UI Symbol", "Noto Music", serif;
  font-size: 64px;
  line-height: 1;
}

.staff-note {
  position: absolute;
  z-index: 4;
  left: var(--note-x, 45%);
  top: var(--note-y, 93px);
  width: 21px;
  height: 15px;
  border-radius: 50%;
  background: var(--note-color, #d25f45);
  transform: translate(-50%, -50%) rotate(-14deg);
  transition: top 380ms var(--ease), left 380ms var(--ease), background 180ms ease;
}

.staff-note::after {
  position: absolute;
  right: 0;
  bottom: 6px;
  width: 2px;
  height: 52px;
  background: var(--note-color, #d25f45);
  content: "";
  transform: rotate(14deg);
  transform-origin: bottom;
}

.staff-note.note-secondary {
  --note-color: #167e77;
}

.staff-note-label {
  position: absolute;
  top: calc(var(--note-y, 93px) + 28px);
  left: var(--note-x, 45%);
  color: #4a5158;
  font-size: 11px;
  font-weight: 700;
  transform: translateX(-50%);
  transition: top 380ms var(--ease), left 380ms var(--ease);
}

.piano {
  position: relative;
  display: flex;
  width: 100%;
  min-height: 154px;
  overflow: hidden;
  border: 1px solid #b8c0c5;
  border-bottom-width: 4px;
  background: #202428;
  isolation: isolate;
}

.piano-key {
  position: relative;
  display: flex;
  align-items: flex-end;
  justify-content: center;
  border: 0;
  cursor: pointer;
  user-select: none;
}

.piano-key.white-key {
  z-index: 1;
  min-width: 0;
  flex: 1;
  padding: 0 1px 10px;
  border-right: 1px solid #bfc5c9;
  background: #fff;
  color: #6c7379;
}

.piano-key.white-key:last-of-type {
  border-right: 0;
}

.piano-key.black-key {
  position: absolute;
  z-index: 3;
  top: 0;
  left: var(--key-left);
  width: 5.1%;
  height: 62%;
  padding: 0 1px 8px;
  border: 1px solid #070809;
  border-radius: 0 0 3px 3px;
  background: #202428;
  color: #d1d5d8;
  transform: translateX(-50%);
}

.piano-key span {
  overflow: hidden;
  font-size: 9px;
  text-overflow: clip;
}

.piano-key:hover,
.piano-key.is-active {
  background: var(--key-color, #e37c61);
  color: #fff;
}

.piano-key.black-key:hover,
.piano-key.black-key.is-active {
  background: var(--key-color, #167e77);
}

.piano-key:active {
  transform: translateY(2px);
}

.piano-key.black-key:active {
  transform: translate(-50%, 2px);
}

.rhythm-builder {
  display: grid;
  gap: 18px;
}

.rhythm-palette {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 8px;
}

.rhythm-choice {
  display: grid;
  min-height: 70px;
  padding: 7px;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-raised);
  cursor: pointer;
}

.rhythm-choice:hover {
  border-color: var(--ink-soft);
}

.rhythm-symbol {
  font-family: "Segoe UI Symbol", "Noto Music", serif;
  font-size: 27px;
}

.rhythm-choice small {
  color: var(--ink-soft);
  font-size: 9px;
}

.rhythm-timeline {
  position: relative;
  display: flex;
  min-height: 112px;
  overflow: hidden;
  border: 1px solid var(--line-strong);
  background:
    linear-gradient(to right, transparent calc(25% - 1px), var(--line) calc(25% - 1px) 25%, transparent 25% calc(50% - 1px), var(--line) calc(50% - 1px) 50%, transparent 50% calc(75% - 1px), var(--line) calc(75% - 1px) 75%, transparent 75%),
    var(--surface-raised);
}

.rhythm-event {
  display: grid;
  width: calc(var(--beats) * 25%);
  min-width: 8%;
  place-content: center;
  border-right: 1px solid var(--line-strong);
  color: var(--ink);
  text-align: center;
}

.rhythm-event.is-rest {
  color: var(--ink-faint);
  background: var(--surface-soft);
}

.rhythm-event strong {
  font-family: "Segoe UI Symbol", "Noto Music", serif;
  font-size: 30px;
  font-weight: 400;
}

.rhythm-event small {
  margin-top: 6px;
  font-size: 9px;
}

.rhythm-playhead {
  position: absolute;
  z-index: 4;
  top: 0;
  bottom: 0;
  left: 0;
  width: 3px;
  background: var(--coral);
  opacity: 0;
  pointer-events: none;
}

.rhythm-playhead.is-playing {
  opacity: 1;
  animation: playhead var(--play-duration, 4s) linear forwards;
}

@keyframes playhead {
  from { left: 0; }
  to { left: 100%; }
}

.range-field {
  display: grid;
  min-width: 160px;
  gap: 5px;
}

.range-field input {
  accent-color: var(--coral);
}

.interval-equation {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  margin: 12px 0;
  color: var(--ink-soft);
  font-family: Georgia, serif;
  font-size: 18px;
}

.interval-equation strong {
  color: var(--coral);
  font-size: 28px;
}

.step-pattern {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px;
  margin-top: 14px;
}

.step-node {
  display: inline-grid;
  min-width: 30px;
  height: 30px;
  place-items: center;
  border-radius: 50%;
  background: var(--teal-soft);
  color: var(--teal);
  font-size: 10px;
  font-weight: 800;
}

.step-arrow {
  color: var(--ink-faint);
  font-size: 10px;
}

.chord-stack {
  position: relative;
  display: grid;
  min-height: 260px;
  place-content: center;
}

.chord-note {
  display: grid;
  width: 154px;
  height: 45px;
  margin-top: -1px;
  place-items: center;
  border: 1px solid var(--line-strong);
  background: var(--surface-raised);
  color: var(--ink);
  font-family: Georgia, serif;
  font-size: 18px;
  font-weight: 700;
  transition: transform 420ms var(--ease), background 220ms ease;
}

.chord-note:first-child {
  border-radius: var(--radius) var(--radius) 0 0;
}

.chord-note:last-child {
  border-radius: 0 0 var(--radius) var(--radius);
}

.chord-note.is-bass {
  border-color: var(--coral);
  background: var(--coral-soft);
  color: var(--coral);
}

.function-flow {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 20px;
  align-items: center;
  margin: 28px 0;
}

.function-node {
  position: relative;
  display: grid;
  min-height: 120px;
  padding: 16px;
  place-content: center;
  border: 1px solid var(--line);
  background: var(--surface-raised);
  text-align: center;
}

.function-node::after {
  position: absolute;
  top: 50%;
  right: -17px;
  color: var(--ink-faint);
  content: "→";
  transform: translateY(-50%);
}

.function-node:last-child::after {
  content: none;
}

.function-node.is-active {
  border-color: var(--node-color, var(--coral));
  box-shadow: inset 0 -4px 0 var(--node-color, var(--coral));
}

.function-node strong {
  color: var(--node-color, var(--ink));
  font-family: Georgia, serif;
  font-size: 24px;
}

.function-node span {
  margin-top: 7px;
  color: var(--ink-soft);
  font-size: 10px;
}

.mode-wheel {
  position: relative;
  width: min(330px, 100%);
  aspect-ratio: 1;
  margin: 0 auto;
  border: 1px solid var(--line);
  border-radius: 50%;
}

.mode-center {
  position: absolute;
  top: 50%;
  left: 50%;
  display: grid;
  width: 42%;
  aspect-ratio: 1;
  place-content: center;
  border-radius: 50%;
  background: var(--surface-strong);
  color: #fff;
  text-align: center;
  transform: translate(-50%, -50%);
}

.mode-center strong {
  font-family: "STSong", "SimSun", serif;
  font-size: 36px;
}

.mode-center small {
  color: #bdc5cb;
  font-size: 10px;
}

.mode-tone {
  position: absolute;
  top: 50%;
  left: 50%;
  display: grid;
  width: 46px;
  height: 46px;
  place-content: center;
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  background: var(--surface-raised);
  color: var(--ink);
  font-size: 12px;
  font-weight: 800;
  transform: translate(-50%, -50%) rotate(var(--tone-angle)) translateY(-125px) rotate(calc(-1 * var(--tone-angle)));
}

.mode-tone.is-root {
  border-color: var(--coral);
  background: var(--coral-soft);
  color: var(--coral);
}

.clue-list {
  display: grid;
  gap: 0;
  margin-bottom: 20px;
  border-top: 1px solid var(--line);
}

.clue-item {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  gap: 12px;
  padding: 14px 0;
  border-bottom: 1px solid var(--line);
}

.clue-number {
  display: grid;
  width: 28px;
  height: 28px;
  place-items: center;
  border-radius: 50%;
  background: var(--blue-soft);
  color: var(--blue);
  font-size: 10px;
  font-weight: 800;
}

.clue-item strong {
  display: block;
  margin-bottom: 3px;
  font-size: 12px;
}

.clue-item p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 11px;
  line-height: 1.6;
}

.quiz-result {
  min-height: 48px;
  margin-top: 14px;
  padding: 12px 14px;
  border-left: 3px solid var(--line-strong);
  background: var(--surface-soft);
  color: var(--ink-soft);
  font-size: 12px;
  line-height: 1.65;
}

.quiz-result.is-correct {
  border-left-color: var(--green);
  color: var(--green);
}

.quiz-result.is-wrong {
  border-left-color: var(--danger);
  color: var(--danger);
}

.translation-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 24px;
}

.notation-panel {
  min-width: 0;
  padding-top: 14px;
  border-top: 2px solid var(--panel-color, var(--blue));
}

.notation-panel h3 {
  margin: 0 0 14px;
  font-size: 13px;
}

.notation-sequence {
  display: flex;
  min-height: 96px;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  padding: 14px;
  border: 1px solid var(--line);
  background: var(--surface-raised);
}

.notation-note {
  display: grid;
  min-width: 34px;
  height: 38px;
  padding: 0 6px;
  place-items: center;
  border: 0;
  border-bottom: 2px solid var(--line-strong);
  background: transparent;
  color: var(--ink);
  cursor: pointer;
  font-family: Georgia, serif;
  font-size: 15px;
}

.notation-note:hover,
.notation-note.is-active {
  border-bottom-color: var(--panel-color, var(--blue));
  color: var(--panel-color, var(--blue));
}

.notation-sequence.is-hidden .notation-note {
  color: transparent;
  text-shadow: 0 0 7px var(--ink-faint);
}

.reveal-item {
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 380ms var(--ease), transform 380ms var(--ease);
}

.reveal-item.is-revealed {
  opacity: 1;
  transform: translateY(0);
}

.slide-enter {
  animation: slide-enter 420ms var(--ease) both;
}

@keyframes slide-enter {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 1120px) {
  .slide-inner {
    padding: 34px 36px 30px;
  }

  .slide-title {
    font-size: 32px;
  }

  .content-grid.cols-4,
  .practice-grid {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .function-flow {
    gap: 14px;
  }
}

@media (max-width: 900px) {
  :root {
    --sidebar-width: 286px;
  }

  .topbar {
    grid-template-columns: 48px auto minmax(0, 1fr) auto;
  }

  .mobile-only {
    display: inline-grid;
    margin-left: 6px;
  }

  .brand {
    align-self: auto;
    padding: 0 10px;
    background: transparent;
    color: var(--ink);
  }

  .brand-mark {
    border-color: var(--line);
    color: var(--coral);
  }

  .brand-copy small {
    color: var(--ink-soft);
  }

  .current-context {
    justify-content: flex-end;
    padding: 0 8px;
  }

  .phase-label,
  .context-divider {
    display: none;
  }

  .workspace {
    grid-template-columns: minmax(0, 1fr);
  }

  .sidebar {
    position: fixed;
    z-index: 35;
    top: var(--topbar-height);
    bottom: 0;
    left: 0;
    width: var(--sidebar-width);
    transform: translateX(-102%);
    transition: transform 260ms var(--ease);
  }

  .sidebar.is-open {
    transform: translateX(0);
  }

  .sidebar-scrim.is-visible {
    display: block;
  }

  .stage-wrap {
    padding: 18px;
  }

  .slide-surface {
    min-height: min(650px, 100%);
  }

  .slide-body.split-layout,
  .lab-stage {
    grid-template-columns: minmax(0, 1fr);
  }

  .lab-readout {
    padding: 18px 0 0;
    border-top: 1px solid var(--line);
    border-left: 0;
  }

  .hero-slide {
    min-height: 600px;
  }

  .hero-title {
    font-size: 48px;
  }
}

@media (max-width: 640px) {
  :root {
    --topbar-height: 58px;
    --controlbar-height: 64px;
  }

  .topbar {
    grid-template-columns: 48px minmax(0, 1fr) auto;
  }

  .brand {
    min-width: 0;
  }

  .brand-mark {
    width: 30px;
    height: 30px;
  }

  .brand-copy {
    min-width: 0;
  }

  .brand-copy strong {
    overflow: hidden;
    font-size: 13px;
    text-overflow: ellipsis;
    white-space: nowrap;
  }

  .brand-copy small,
  .current-context,
  #themeButton {
    display: none;
  }

  .stage-wrap {
    align-items: stretch;
    padding: 8px;
  }

  .slide-surface {
    width: 100%;
    min-height: 100%;
    border-radius: 3px;
    box-shadow: none;
  }

  .slide-inner {
    padding: 28px 22px 24px;
  }

  .slide-header {
    grid-template-columns: minmax(0, 1fr);
    gap: 4px;
    margin-bottom: 20px;
  }

  .slide-title {
    font-size: 27px;
    line-height: 1.3;
  }

  .slide-lead {
    font-size: 13px;
    line-height: 1.75;
  }

  .source-page {
    text-align: left;
  }

  .hero-slide {
    min-height: 100%;
    padding: 38px 24px;
  }

  .hero-title {
    font-size: 40px;
    line-height: 1.25;
  }

  .hero-subtitle {
    font-size: 14px;
  }

  .content-grid,
  .content-grid.cols-3,
  .content-grid.cols-4,
  .practice-grid,
  .standards,
  .translation-grid {
    grid-template-columns: minmax(0, 1fr);
  }

  .formula-band {
    align-items: flex-start;
    flex-direction: column;
    gap: 8px;
  }

  .formula-value {
    font-size: 19px;
  }

  .media-frame {
    padding: 10px;
  }

  .media-frame img {
    max-height: 280px;
  }

  .controlbar {
    grid-template-columns: 42px minmax(0, 1fr) 42px;
    gap: 8px;
    padding: 8px 10px;
  }

  .nav-button {
    width: 42px;
    height: 42px;
  }

  .page-context {
    display: none;
  }

  .reveal-button {
    min-width: 0;
    justify-self: stretch;
  }

  .rhythm-palette {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .piano {
    min-height: 128px;
  }

  .piano-key span {
    font-size: 8px;
  }

  .staff-lines {
    right: 14px;
    left: 38px;
  }

  .clef-symbol {
    left: 41px;
  }

  .function-flow {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .function-node::after {
    content: none;
  }

  .mode-tone {
    width: 42px;
    height: 42px;
    transform: translate(-50%, -50%) rotate(var(--tone-angle)) translateY(-105px) rotate(calc(-1 * var(--tone-angle)));
  }

  [data-tooltip]::after {
    content: none;
  }

  .toast {
    bottom: 76px;
  }
}

@media (max-height: 760px) and (min-width: 901px) {
  .stage-wrap {
    padding-top: 14px;
    padding-bottom: 14px;
  }

  .slide-inner {
    padding-top: 30px;
    padding-bottom: 26px;
  }

  .slide-header {
    margin-bottom: 20px;
  }

  .hero-slide {
    min-height: 540px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    animation-duration: 1ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 1ms !important;
  }
}