:root {
  color-scheme: dark;
  --bg: #132724;
  --surface: #1a332f;
  --surface-raised: #24423c;
  --surface-soft: #172e2a;
  --ink: #f2ebdd;
  --muted: #bdc8c0;
  --faint: #879b93;
  --line: rgba(240, 235, 220, 0.15);
  --line-strong: rgba(240, 235, 220, 0.32);
  --accent: #e28d78;
  --accent-strong: #f1a18b;
  --accent-ink: #142521;
  --secondary: #82b2a6;
  --signal: #d9b96c;
  --password-strength-yellow: #e0bd54;
  --danger: #e47d79;
  --success: #69aa8c;
  --shadow: 0 20px 55px rgba(5, 14, 13, 0.28);
  --radius: 6px;
  --font-ui: "IBM Plex Sans SC", "Microsoft YaHei UI", sans-serif;
  --font-display: "IBM Plex Sans SC", "Microsoft YaHei UI", sans-serif;
  --font-reading: "IBM Plex Sans SC", "Microsoft YaHei UI", sans-serif;
  --content-width: 920px;
  --appbar-height: 72px;
}

body[data-theme="mist"] {
  color-scheme: light;
  --bg: #f1f3ef;
  --surface: #f9faf7;
  --surface-raised: #ffffff;
  --surface-soft: #e4e9e3;
  --ink: #222927;
  --muted: #626d68;
  --faint: #63706a;
  --line: rgba(34, 41, 39, 0.12);
  --line-strong: rgba(34, 41, 39, 0.28);
  --accent: #477c6c;
  --accent-strong: #32675a;
  --accent-ink: #ffffff;
  --secondary: #ba5d4e;
  --signal: #4f5e8c;
  --password-strength-yellow: #8a6500;
  --danger: #b94745;
  --success: #397b60;
  --shadow: 0 18px 48px rgba(35, 48, 43, 0.1);
  --radius: 5px;
  --font-ui: "LXGW WenKai Screen R", "Microsoft YaHei UI", sans-serif;
  --font-display: "LXGW WenKai Screen R", "Microsoft YaHei UI", sans-serif;
  --font-reading: "LXGW WenKai Screen R", "Microsoft YaHei UI", sans-serif;
}

body[data-theme="clay"] {
  color-scheme: light;
  --bg: #e9dfd6;
  --surface: #f1e9e1;
  --surface-raised: #faf5ef;
  --surface-soft: #dccdc2;
  --ink: #342f30;
  --muted: #66595a;
  --faint: #695c5c;
  --line: rgba(52, 47, 48, 0.13);
  --line-strong: rgba(52, 47, 48, 0.3);
  --accent: #a95752;
  --accent-strong: #91433f;
  --accent-ink: #ffffff;
  --secondary: #376f70;
  --signal: #65517f;
  --password-strength-yellow: #8a6500;
  --danger: #9f3d3f;
  --success: #2f675c;
  --shadow: 0 20px 52px rgba(67, 49, 47, 0.14);
  --radius: 7px;
  --font-ui: "Noto Serif SC Variable", "Source Han Serif SC", SimSun, serif;
  --font-display: "Noto Serif SC Variable", "Source Han Serif SC", SimSun, serif;
  --font-reading: "Noto Serif SC Variable", "Source Han Serif SC", SimSun, serif;
}

* {
  box-sizing: border-box;
}

html {
  min-width: 320px;
  background: var(--bg);
}

body {
  margin: 0;
  min-width: 320px;
  min-height: 100vh;
  overflow-x: hidden;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-ui);
  font-size: 16px;
  line-height: 1.65;
  letter-spacing: 0;
  transition: background-color 220ms ease, color 220ms ease;
}

button,
input,
textarea,
select {
  color: inherit;
  font: inherit;
  letter-spacing: 0;
}

button {
  cursor: pointer;
}

button:disabled {
  cursor: not-allowed;
  opacity: 0.45;
}

button:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible {
  outline: 3px solid var(--ink);
  outline-offset: 3px;
}

button svg,
.drawer-section-title svg {
  display: block;
  width: 20px;
  height: 20px;
  flex: 0 0 auto;
  stroke-width: 1.8;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1,
h2,
h3 {
  font-family: var(--font-display);
  font-weight: 650;
  line-height: 1.2;
}

.hidden,
.compat-actions,
.compat-control {
  display: none !important;
}

.is-invisible {
  visibility: hidden !important;
  pointer-events: none !important;
}

.visually-hidden {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

.app-shell,
.study-view {
  min-height: 100vh;
}

.kicker,
.stage-index {
  display: block;
  margin-bottom: 8px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  line-height: 1.25;
  text-transform: uppercase;
}

.primary-button,
.secondary-button,
.danger-button,
.text-button,
.icon-button,
.primary-nav button,
.theme-picker button,
.topic-item {
  border: 0;
  border-radius: var(--radius);
  transition: background-color 160ms ease, border-color 160ms ease, color 160ms ease, transform 160ms ease, opacity 160ms ease;
}

.primary-button,
.secondary-button,
.danger-button {
  min-height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 11px 18px;
  font-weight: 700;
}

.primary-button {
  background: var(--accent);
  color: var(--accent-ink);
}

.primary-button:hover:not(:disabled) {
  background: var(--accent-strong);
  transform: translateY(-1px);
}

.secondary-button {
  border: 1px solid var(--line-strong);
  background: transparent;
  color: var(--ink);
}

.secondary-button:hover:not(:disabled) {
  background: var(--surface-soft);
}

.danger-button {
  border: 1px solid color-mix(in srgb, var(--danger) 50%, transparent);
  background: transparent;
  color: var(--danger);
}

.danger-button:hover:not(:disabled) {
  background: color-mix(in srgb, var(--danger) 12%, transparent);
}

.text-button {
  padding: 7px 8px;
  background: transparent;
  color: var(--muted);
  font-size: 13px;
}

.text-button:hover {
  color: var(--ink);
}

.icon-button {
  width: 44px;
  height: 44px;
  display: inline-grid;
  place-items: center;
  padding: 0;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--ink);
}

.icon-button:hover:not(:disabled) {
  border-color: var(--line-strong);
  background: var(--surface-soft);
}

.icon-button.small {
  width: 34px;
  height: 34px;
}

.field {
  display: grid;
  gap: 8px;
}

.field label,
.compact-field label {
  font-size: 14px;
  font-weight: 700;
}

input,
textarea,
select {
  width: 100%;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--surface-raised) 88%, transparent);
  color: var(--ink);
}

input,
select {
  min-height: 48px;
  padding: 0 14px;
}

textarea {
  min-height: 126px;
  padding: 13px 14px;
  line-height: 1.7;
  resize: vertical;
}

input::placeholder,
textarea::placeholder {
  color: var(--faint);
}

.message {
  min-height: 1.5em;
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}

.input-hint,
.scale-hint,
.outline-note {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
}

.password-strength {
  display: grid;
  gap: 7px;
}

.password-strength-track {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 5px;
}

.password-strength-track span {
  height: 4px;
  border-radius: 99px;
  background: var(--line-strong);
}

.password-strength p {
  display: flex;
  flex-wrap: wrap;
  gap: 5px 10px;
  margin: 0;
  color: var(--muted);
  font-size: 12px;
}

.password-strength strong {
  color: var(--muted);
  font-weight: 650;
}

.password-strength[data-level="red"] .password-strength-track span:first-child {
  background: var(--danger);
}

.password-strength[data-level="red"] strong {
  color: var(--danger);
}

.password-strength[data-level="yellow"] .password-strength-track span:nth-child(-n + 2) {
  background: var(--password-strength-yellow);
}

.password-strength[data-level="yellow"] strong {
  color: var(--password-strength-yellow);
}

.password-strength[data-level="green"] .password-strength-track span {
  background: var(--success);
}

.password-strength[data-level="green"] strong {
  color: var(--success);
}

/* 首次进入：积木小人沿台阶走向 2 SIGMA，后续访问直接显示登录。 */
.auth-view {
  position: relative;
  min-height: 100vh;
  display: grid;
  grid-template-columns: minmax(280px, 0.9fr) minmax(360px, 480px);
  align-items: center;
  gap: clamp(40px, 8vw, 130px);
  padding: clamp(24px, 6vw, 84px);
  overflow: hidden;
}

.site-compliance {
  position: absolute;
  z-index: 4;
  right: 18px;
  bottom: max(12px, env(safe-area-inset-bottom));
  left: 18px;
  text-align: center;
}

.site-compliance a {
  color: var(--muted);
  font-size: 13px;
  text-underline-offset: 3px;
}

.auth-copy {
  position: relative;
  z-index: 2;
  max-width: 680px;
  opacity: 1;
  transform: translateY(0);
  transition: opacity 420ms ease, transform 420ms ease;
}

.auth-copy h1 {
  max-width: 640px;
  margin-bottom: 20px;
  font-family: var(--font-display);
  font-size: 52px;
  font-weight: 650;
}

.auth-copy h1 span {
  display: block;
}

.auth-theme-picker {
  width: max-content;
  margin-top: 24px;
}

.auth-theme-picker button {
  width: 58px;
  min-height: 46px;
  padding: 7px;
  border-radius: 4px;
}

.auth-theme-picker .theme-swatch {
  width: 42px;
  height: 28px;
}

.auth-panel {
  position: relative;
  z-index: 3;
  display: grid;
  gap: 18px;
  padding: clamp(24px, 4vw, 38px);
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--surface-raised);
  box-shadow: var(--shadow);
  opacity: 1;
  transform: translateY(0);
  transition: opacity 420ms ease 100ms, transform 420ms ease 100ms;
}

.segmented {
  display: grid;
  grid-template-columns: 1fr 1fr;
  padding: 4px;
  border-radius: var(--radius);
  background: var(--surface-soft);
}

.segmented button {
  min-height: 40px;
  border: 0;
  border-radius: calc(var(--radius) - 2px);
  background: transparent;
  color: var(--muted);
  font-weight: 700;
}

.segmented button.active {
  background: var(--surface-raised);
  color: var(--ink);
  box-shadow: 0 3px 12px color-mix(in srgb, var(--ink) 9%, transparent);
}

.entry-scene {
  position: absolute;
  inset: 0;
  z-index: 0;
  overflow: hidden;
  pointer-events: none;
  opacity: 0.34;
  transition: opacity 480ms ease;
}

.visual-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.visual-fallback {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  color: var(--signal);
}

.webgl-ready .visual-fallback {
  display: none;
}

.entry-fallback strong {
  position: absolute;
  font-family: var(--font-display);
  font-size: clamp(44px, 8vw, 88px);
  letter-spacing: 0;
}

.fallback-orbit {
  display: none;
}

.intro-scene-caption {
  position: absolute;
  left: clamp(20px, 5vw, 70px);
  bottom: clamp(18px, 5vw, 60px);
  display: grid;
  gap: 2px;
  margin: 0;
  color: var(--muted);
  font-size: 12px;
  opacity: 0;
  transition: opacity 280ms ease;
}

.intro-scene-caption strong {
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 500;
}

body.intro-pending .auth-copy,
body.intro-pending .auth-panel {
  opacity: 0;
  transform: translateY(20px);
  pointer-events: none;
}

body.intro-pending .entry-scene {
  opacity: 1;
}

body.intro-pending .intro-scene-caption {
  opacity: 1;
}

.skip-intro {
  position: fixed;
  top: 18px;
  right: 20px;
  z-index: 8;
}

body:not(.intro-pending) .skip-intro {
  display: none;
}

.appbar {
  position: sticky;
  top: 0;
  z-index: 30;
  min-height: var(--appbar-height);
  display: grid;
  grid-template-columns: 44px minmax(0, 1fr) auto 44px;
  align-items: center;
  gap: 14px;
  padding: 10px clamp(14px, 4vw, 54px);
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 93%, transparent);
  backdrop-filter: blur(18px);
}

.appbar-heading {
  min-width: 0;
}

.appbar-heading .kicker {
  margin-bottom: 1px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.appbar-heading h1 {
  margin: 0;
  overflow: hidden;
  font-size: 17px;
  font-weight: 700;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.appbar-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--muted);
  font-size: 13px;
}

.connection-dot {
  display: flex;
  align-items: center;
  gap: 6px;
}

.connection-dot::before {
  content: "";
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--secondary);
}

.lesson-count {
  min-width: 54px;
  text-align: right;
}

.stage-shell {
  min-height: calc(100vh - var(--appbar-height));
  display: grid;
}

.stage {
  width: min(100%, 1280px);
  min-height: calc(100vh - var(--appbar-height));
  margin: 0 auto;
  padding: clamp(28px, 6vh, 72px) clamp(18px, 5vw, 68px);
  animation: stage-enter 300ms ease both;
}

.stage-heading {
  max-width: 760px;
  margin-bottom: 36px;
}

.stage-heading h2,
.stage-copy h2 {
  margin-bottom: 14px;
  font-family: var(--font-display);
  font-size: 36px;
}

.stage-heading p,
.stage-copy p {
  color: var(--muted);
  font-size: 17px;
}

@keyframes stage-enter {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.empty-stage {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: flex-start;
}

.stage-copy {
  max-width: 660px;
}

.stage-copy .primary-button {
  margin-top: 18px;
}

.topic-stage {
  display: grid;
  place-items: start center;
}

.topic-form {
  width: min(100%, 760px);
  display: grid;
  gap: 24px;
}

.field-large input {
  min-height: 58px;
  font-size: 18px;
}

.compact-field {
  max-width: 360px;
}

.learning-period-field {
  width: min(100%, 420px);
  max-width: 420px;
}

.learning-period-controls {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 100px;
  gap: 10px;
}

.topic-form > .primary-button {
  justify-self: start;
  min-width: 210px;
}

.early-access-panel {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 24px;
  padding: 20px 22px;
  border-block: 1px solid var(--line);
  background: color-mix(in srgb, var(--accent) 8%, transparent);
}

.early-access-panel h3 {
  margin: 0 0 5px;
  font-family: var(--font-display);
  font-size: 20px;
}

.early-access-panel p,
.dialog-lead {
  margin: 0;
  color: var(--muted);
}

.early-access-panel .secondary-button {
  white-space: nowrap;
}

.compact-price {
  margin-bottom: 0;
}

.compact-price strong {
  font-size: 34px;
}

.pending-stage {
  display: grid;
  grid-template-columns: minmax(300px, 0.96fr) minmax(320px, 0.72fr);
  align-items: center;
  gap: clamp(30px, 6vw, 92px);
}

.journey-visual {
  position: relative;
  display: grid;
  place-items: center;
  width: min(51vw, 620px);
  min-width: 300px;
  aspect-ratio: 1.12;
  min-height: 360px;
  overflow: hidden;
}

.journey-fallback {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
}

.journey-fallback span {
  width: 34px;
  height: 22px;
  border: 1px solid var(--line-strong);
  background: var(--surface-raised);
}

.journey-fallback span:nth-child(2) { background: var(--secondary); transform: translateY(-14px); }
.journey-fallback span:nth-child(3) { background: var(--signal); transform: translateY(-28px); }
.journey-fallback span:nth-child(4) { background: var(--accent); transform: translateY(-14px); }
.journey-fallback span:nth-child(5) { transform: translateY(0); }

.pending-copy {
  width: min(100%, 390px);
  max-width: 390px;
}

.pending-copy h2 {
  margin-bottom: 10px;
  font-family: var(--font-display);
  font-size: 32px;
}

.pending-copy > p {
  color: var(--muted);
}

.pending-copy .pending-elapsed {
  margin: 46px 0 0;
  color: var(--faint);
  font-size: 13px;
  font-weight: 400;
  letter-spacing: 0.075em;
}

.wait-note {
  min-height: 166px;
  margin: 0;
  padding: 0;
}

.wait-note .waiting-primary-copy {
  margin: 0;
  font-family: var(--font-reading);
  font-size: clamp(24px, 2.45vw, 31px);
  font-weight: 540;
  line-height: 1.72;
  letter-spacing: 0.035em;
}

.waiting-primary-copy > span {
  display: block;
  max-width: 100%;
  overflow-wrap: anywhere;
  white-space: normal;
}

.wait-note .waiting-source-copy {
  margin: 19px 0 0;
  color: color-mix(in srgb, var(--ink) 66%, transparent);
  font-size: 15px;
  line-height: 1.6;
  letter-spacing: 0.025em;
}

.wait-note p.tip-enter {
  animation: tip-enter 320ms ease both;
}

@keyframes tip-enter {
  from { opacity: 0; transform: translateY(5px); }
  to { opacity: 1; transform: translateY(0); }
}

.review-stage {
  width: min(100%, 920px);
}

.review-content {
  font-size: 18px;
}

.next-lesson-notice {
  margin: 24px 0 0;
  padding: 14px 16px;
  border-left: 3px solid var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, transparent);
  color: var(--ink);
  line-height: 1.75;
}

.expert-roundtable-entry {
  display: flex;
  align-items: center;
  margin-top: 30px;
  padding: 18px 0;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}

.review-next {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: 24px;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--line-strong);
  color: var(--muted);
}

.review-next .primary-button {
  flex: 0 0 auto;
  min-width: 140px;
}

.learning-stage {
  width: 100%;
  max-width: none;
  min-height: calc(100vh - var(--appbar-height));
  padding: 0;
}

.reader {
  width: min(100%, var(--content-width));
  min-height: calc(100vh - var(--appbar-height));
  margin: 0 auto;
  padding: clamp(28px, 5vw, 62px) clamp(20px, 5vw, 56px) 90px;
}

.lesson-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 28px;
  margin-bottom: 44px;
  padding-bottom: 22px;
  border-bottom: 1px solid var(--line-strong);
}

.lesson-heading {
  min-width: 0;
}

.lesson-heading span {
  display: block;
  margin-bottom: 7px;
  overflow: hidden;
  color: var(--muted);
  font-size: 13px;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.lesson-heading h2 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 30px;
}

.respond-button {
  flex: 0 0 auto;
}

.lesson-scroll {
  min-width: 0;
}

.markdown {
  overflow-wrap: anywhere;
}

.ai-badge {
  display: inline-block;
  margin: 0 0 12px;
  color: var(--muted);
  font-size: 11px;
  font-weight: 500;
  line-height: 1;
  letter-spacing: 0.12em;
  opacity: 0.48;
}

.markdown > :first-child {
  margin-top: 0;
}

.markdown > :last-child {
  margin-bottom: 0;
}

.course-content,
.opening-story .markdown {
  font-family: var(--font-reading);
  font-size: 18px;
  line-height: 1.95;
}

.markdown h1,
.markdown h2,
.markdown h3,
.markdown h4 {
  margin: 1.7em 0 0.65em;
  color: var(--ink);
  font-family: var(--font-reading);
}

.markdown h1 { font-size: 28px; }
.markdown h2 { font-size: 23px; }
.markdown h3 { font-size: 19px; }

.markdown p,
.markdown ul,
.markdown ol,
.markdown blockquote {
  margin-bottom: 1.1em;
}

.markdown li + li {
  margin-top: 0.45em;
}

.markdown blockquote {
  margin-left: 0;
  padding: 4px 0 4px 18px;
  border-left: 3px solid var(--accent);
  color: var(--muted);
}

.markdown code {
  padding: 2px 5px;
  border-radius: 3px;
  background: var(--surface-soft);
  font-family: Consolas, monospace;
}

.opening-story {
  margin-bottom: 44px;
  padding-bottom: 40px;
  border-bottom: 1px solid var(--line);
}

.section-label {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 18px;
}

.section-label strong {
  font-size: 14px;
}

.section-label span {
  color: var(--muted);
  font-size: 12px;
}

.concept-panel {
  margin-top: 52px;
  padding-top: 26px;
  border-top: 1px solid var(--line-strong);
}

.lesson-response-cta {
  width: 100%;
  margin-top: 48px;
  justify-content: center;
}

.concept-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.concept-buttons button {
  min-height: 38px;
  padding: 7px 12px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: transparent;
  color: var(--ink);
}

.concept-buttons button:hover {
  border-color: var(--accent);
  color: var(--accent-strong);
}

.concept-content {
  margin-top: 24px;
  padding-left: 18px;
  border-left: 3px solid var(--secondary);
}

body[data-stage="response"] .learning-stage {
  display: grid;
  grid-template-columns: minmax(0, 1.12fr) minmax(380px, 0.88fr);
  height: calc(100vh - var(--appbar-height));
  overflow: hidden;
}

body[data-stage="response"] .reader {
  width: 100%;
  min-height: 0;
  height: 100%;
  max-width: none;
  padding: 34px clamp(22px, 4vw, 54px) 52px;
  overflow-y: auto;
  scrollbar-gutter: stable;
}

body[data-stage="response"] .lesson-head {
  margin-bottom: 30px;
}

body[data-stage="response"] .respond-button {
  display: none;
}

body[data-stage="response"] .lesson-response-cta {
  display: none;
}

.answer-panel {
  min-width: 0;
  min-height: 0;
  flex-direction: column;
  border-left: 1px solid var(--line-strong);
  background: var(--surface);
}

body[data-stage="response"] .answer-panel:not(.hidden) {
  display: flex;
}

.answer-scroll {
  min-height: 0;
  flex: 1 1 auto;
  overflow-y: auto;
  padding: 36px clamp(22px, 4vw, 48px) 24px;
  scrollbar-gutter: stable;
}

.answer-heading {
  margin-bottom: 24px;
}

.answer-heading h2 {
  font-size: 28px;
}

.checkpoint {
  margin-bottom: 28px;
  color: var(--ink);
}

.answer-field textarea {
  min-height: 210px;
  background: var(--surface-raised);
}

.answer-actions {
  flex: 0 0 auto;
  display: flex;
  justify-content: flex-end;
  gap: 12px;
  padding: 16px clamp(22px, 4vw, 48px);
  border-top: 1px solid var(--line);
  background: var(--surface);
}

.answer-actions .primary-button {
  min-width: 150px;
}

.paywall-panel {
  width: min(100%, 900px);
}

.price-line {
  display: flex;
  align-items: baseline;
  gap: 14px;
  margin: 0 0 32px;
}

.price-line strong {
  font-family: var(--font-display);
  font-size: 42px;
}

.price-line span {
  color: var(--muted);
}

.paywall-outline {
  margin: 28px 0 34px;
  padding: 24px 0;
  border-top: 1px solid var(--line-strong);
  border-bottom: 1px solid var(--line-strong);
}

.paywall-outline summary {
  cursor: pointer;
  color: var(--ink);
  font-family: var(--font-display);
  font-size: 17px;
  font-weight: 700;
}

.paywall-outline[open] summary {
  margin-bottom: 18px;
}

.outline-title {
  font-weight: 700;
}

.paywall-outline ol {
  display: grid;
  gap: 14px;
  padding-left: 22px;
}

.paywall-outline li strong,
.paywall-outline li span {
  display: block;
}

.paywall-outline li span {
  color: var(--muted);
  font-size: 14px;
}

.choice-field,
.rating-field {
  margin: 0 0 24px;
  padding: 0;
  border: 0;
}

.choice-field legend,
.rating-field legend {
  margin-bottom: 12px;
  font-weight: 700;
}

.choice-list {
  display: grid;
  gap: 10px;
}

.choice-option {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 13px 14px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--surface-raised) 68%, transparent);
}

.choice-option input {
  width: 18px;
  min-height: 18px;
  margin: 3px 0 0;
  accent-color: var(--accent);
}

.paywall-actions,
.dialog-actions {
  display: flex;
  justify-content: flex-end;
  gap: 12px;
  margin-top: 26px;
}

.progress-panel {
  position: relative;
  width: min(100%, 900px);
}

.stage-close {
  position: absolute;
  top: clamp(24px, 6vh, 66px);
  right: clamp(18px, 5vw, 66px);
}

.progress-content {
  padding-left: 22px;
  border-left: 2px solid var(--secondary);
}

.lesson-history-section {
  display: grid;
  gap: 10px;
  margin-bottom: 24px;
}

.lesson-history-section h3,
.history-review-section h3 {
  margin: 0;
}

.lesson-history-list {
  display: grid;
  gap: 8px;
}

.lesson-history-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  color: var(--ink);
  text-align: left;
}

.lesson-history-item:hover,
.lesson-history-item:focus-visible {
  border-color: var(--accent);
}

.lesson-history-item span {
  flex: 0 0 auto;
  color: var(--muted);
  font-size: 0.86rem;
}

.lesson-history-dialog {
  width: min(820px, calc(100vw - 28px));
}

.expert-roundtable-dialog {
  width: min(820px, calc(100vw - 28px));
}

.expert-roundtable-experts {
  display: grid;
  gap: 14px;
}

.expert-roundtable-speech {
  display: grid;
  gap: 8px;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: color-mix(in srgb, var(--surface) 82%, transparent);
}

.expert-roundtable-speech h3,
.expert-roundtable-speech p,
.expert-roundtable-judge h3 {
  margin: 0;
}

.expert-roundtable-speech p {
  color: var(--ink);
  line-height: 1.85;
  white-space: pre-wrap;
}

.expert-roundtable-judge {
  display: grid;
  gap: 10px;
  padding-top: 20px;
  border-top: 1px solid var(--line-strong);
}

.history-review-section {
  display: grid;
  gap: 10px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.history-roundtable-section {
  display: grid;
  gap: 16px;
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.history-roundtable-section > h3 {
  margin: 0;
}

.report-panel {
  width: min(100%, 900px);
  align-content: center;
}

.report-panel .primary-button {
  justify-self: start;
}

.reveal-chunk {
  opacity: 0;
  filter: blur(1px);
  transform: translateY(3px);
  transition:
    opacity 600ms ease var(--reveal-delay, 0ms),
    filter 650ms ease var(--reveal-delay, 0ms),
    transform 650ms ease var(--reveal-delay, 0ms);
}

.reveal-active .reveal-chunk {
  opacity: 1;
  filter: blur(0);
  transform: translateY(0);
}

/* 抽屉与弹窗 */
dialog {
  color: var(--ink);
}

dialog::backdrop {
  background: rgba(7, 12, 11, 0.58);
  backdrop-filter: blur(5px);
}

.drawer-dialog {
  width: min(420px, 94vw);
  height: 100vh;
  max-height: none;
  margin: 0 0 0 auto;
  padding: 0;
  border: 0;
  border-radius: 0;
  background: var(--surface-raised);
  box-shadow: -24px 0 60px rgba(0, 0, 0, 0.22);
}

.drawer-dialog[open] {
  animation: drawer-enter 220ms ease both;
}

@keyframes drawer-enter {
  from { opacity: 0; transform: translateX(24px); }
  to { opacity: 1; transform: translateX(0); }
}

.drawer-body {
  height: 100%;
  display: flex;
  flex-direction: column;
  gap: 24px;
  overflow-y: auto;
  padding: 24px;
}

.drawer-head,
.dialog-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 20px;
}

.drawer-head h2,
.dialog-head h2 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 24px;
}

.primary-nav {
  display: grid;
  gap: 6px;
}

.primary-nav button,
.topic-item {
  width: 100%;
  min-height: 46px;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  background: transparent;
  color: var(--ink);
  text-align: left;
}

.primary-nav button:hover,
.topic-item:hover,
.topic-item.active {
  background: var(--surface-soft);
}

.drawer-section {
  padding-top: 20px;
  border-top: 1px solid var(--line);
}

.drawer-section-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 12px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
}

.topic-list {
  display: grid;
  gap: 6px;
}

.topic-item {
  display: grid;
  gap: 1px;
}

.topic-item strong,
.topic-item span {
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.topic-item span {
  color: var(--muted);
  font-size: 12px;
}

.theme-picker {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
}

.theme-picker button {
  min-width: 0;
  display: grid;
  gap: 7px;
  justify-items: center;
  padding: 8px 4px;
  border: 1px solid transparent;
  background: transparent;
  color: var(--muted);
  font-size: 12px;
}

.theme-picker button small {
  color: var(--faint);
  font-size: 10px;
  line-height: 1.25;
}

.theme-picker button[aria-checked="true"] {
  border-color: var(--line-strong);
  background: var(--surface-soft);
  color: var(--ink);
}

.theme-swatch {
  width: 42px;
  height: 28px;
  display: block;
  border: 1px solid rgba(17, 20, 18, 0.18);
  border-radius: 3px;
  box-shadow: none;
}

.motion-preference {
  justify-self: start;
  margin-top: 12px;
  color: var(--muted);
}

.swatch-valley { background: linear-gradient(90deg, #132724 0 46%, #e28d78 46% 72%, #82b2a6 72%); }
.swatch-mist { background: linear-gradient(90deg, #f1f3ef 0 46%, #477c6c 46% 72%, #ba5d4e 72%); }
.swatch-clay { background: linear-gradient(90deg, #e9dfd6 0 46%, #a95752 46% 72%, #376f70 72%); }

.account-actions {
  margin-top: auto;
  display: grid;
  grid-template-columns: 1fr;
  gap: 8px;
}

.account-actions .secondary-button,
.account-actions .danger-button {
  width: 100%;
}

.account-cancel-button {
  border-color: var(--danger);
  background: var(--danger);
  color: var(--accent-ink);
}

.account-cancel-button:hover:not(:disabled) {
  background: color-mix(in srgb, var(--danger) 88%, var(--ink));
  border-color: color-mix(in srgb, var(--danger) 88%, var(--ink));
  transform: translateY(-1px);
}

.dialog {
  width: min(620px, calc(100vw - 28px));
  max-height: calc(100vh - 28px);
  padding: 0;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: var(--surface-raised);
  box-shadow: var(--shadow);
}

.wide-dialog {
  width: min(760px, calc(100vw - 28px));
}

.learning-map-dialog {
  width: min(680px, calc(100vw - 28px));
}

.learning-map-body {
  gap: 18px;
}

.learning-map-body .eyebrow {
  margin: 0 0 4px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.learning-map-current,
.learning-map-goal,
.learning-map-forecast {
  padding: 18px 20px;
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface-soft) 74%, transparent);
}

.map-label,
.learning-map-forecast h3 {
  margin: 0 0 8px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 800;
}

.map-current-title,
.learning-map-goal > p:last-child {
  margin: 0;
  line-height: 1.7;
}

.map-current-title {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
}

.learning-map-forecast ol {
  display: grid;
  gap: 10px;
  margin: 0;
  padding-left: 24px;
}

.learning-map-forecast li {
  padding-left: 4px;
  line-height: 1.65;
}

.learning-map-note {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.6;
}

.dialog-body {
  display: grid;
  gap: 20px;
  max-height: calc(100vh - 30px);
  overflow-y: auto;
  padding: clamp(22px, 5vw, 36px);
}

.support-dialog {
  width: min(620px, calc(100vw - 28px));
}

.support-body {
  grid-template-rows: auto minmax(160px, 1fr) auto auto auto;
}

.support-history {
  min-height: 180px;
  max-height: min(48vh, 480px);
  display: grid;
  align-content: start;
  gap: 14px;
  overflow-y: auto;
  padding: 4px;
}

.support-empty {
  margin: auto 0;
  color: var(--muted);
  text-align: center;
}

.support-case {
  display: grid;
  gap: 8px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--line);
}

.support-case:last-child {
  padding-bottom: 0;
  border-bottom: 0;
}

.support-message {
  width: fit-content;
  max-width: 88%;
  margin: 0;
  padding: 10px 12px;
  border-radius: 12px;
  background: var(--surface-soft);
  line-height: 1.65;
  white-space: pre-wrap;
}

.support-message-user {
  justify-self: end;
  background: var(--accent);
  color: var(--accent-ink);
}

.support-message-human {
  border: 1px solid var(--line-strong);
}

.support-message-system {
  color: var(--muted);
  font-size: 13px;
}

.support-compose {
  margin: 0;
}

.support-account-summary {
  justify-self: start;
  margin: -6px 0 -4px;
}

.account-center-dialog {
  width: min(660px, calc(100vw - 28px));
}

.account-center-body {
  gap: 22px;
}

.account-center-body .eyebrow,
.account-entitlement .eyebrow {
  margin: 0 0 4px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
}

.account-overview {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}

.account-overview > div,
.account-entitlement,
.account-recovery,
.account-password {
  border: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface-soft) 72%, transparent);
}

.account-overview > div {
  min-width: 0;
  display: grid;
  gap: 4px;
  padding: 15px 16px;
}

.account-overview span {
  color: var(--muted);
  font-size: 12px;
}

.account-overview strong {
  overflow-wrap: anywhere;
}

.account-entitlement,
.account-recovery,
.account-password {
  padding: 18px 20px;
}

.account-entitlement h3,
.account-recovery h3,
.account-password h3 {
  margin: 0;
  font-family: var(--font-display);
  font-size: 18px;
}

.account-entitlement > p:last-child,
.account-recovery p {
  margin: 8px 0 0;
  color: var(--muted);
}

.account-password {
  display: grid;
  gap: 16px;
}

.account-password > div:first-child .input-hint {
  margin-top: 5px;
}

.account-password .field {
  margin: 0;
}

.account-password .primary-button {
  justify-self: start;
}

.account-notification-dialog {
  width: min(520px, calc(100vw - 28px));
}

.account-notification-body {
  gap: 24px;
}

.account-notification-text {
  margin: 0;
  color: var(--ink);
  font-size: clamp(17px, 2.4vw, 20px);
  line-height: 1.8;
  white-space: pre-wrap;
}

.account-notification-body .primary-button {
  justify-self: end;
}

.teachability-content h2 {
  font-family: var(--font-display);
}

.suggestion-list {
  display: grid;
  gap: 10px;
  margin: 18px 0;
}

.suggestion-item {
  width: 100%;
  display: grid;
  gap: 4px;
  justify-items: start;
  text-align: left;
}

.suggestion-item span {
  color: var(--muted);
  font-size: 13px;
}

.rating-row {
  display: grid;
  grid-template-columns: repeat(6, minmax(42px, 1fr));
  gap: 8px;
}

.rating-row label {
  min-width: 0;
}

.rating-row input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.rating-row span {
  min-height: 42px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius);
  background: transparent;
}

.rating-row input:checked + span {
  border-color: var(--accent);
  background: var(--accent);
  color: var(--accent-ink);
}

.app-toast {
  position: fixed;
  z-index: 120;
  left: 50%;
  bottom: max(24px, env(safe-area-inset-bottom));
  max-width: min(520px, calc(100vw - 32px));
  padding: 12px 16px;
  border: 1px solid var(--line-strong);
  border-radius: 6px;
  background: var(--ink);
  color: var(--surface);
  box-shadow: 0 12px 32px color-mix(in srgb, var(--ink) 20%, transparent);
  opacity: 0;
  pointer-events: none;
  transform: translate(-50%, 10px);
  transition: opacity 180ms ease, transform 180ms ease;
}

.app-toast.visible {
  opacity: 1;
  transform: translate(-50%, 0);
}

@media (max-width: 900px) {
  .auth-view {
    grid-template-columns: 1fr;
    align-content: center;
    gap: 32px;
  }

  .auth-copy {
    max-width: 520px;
  }

  .auth-copy h1 {
    font-size: 38px;
  }

  .auth-panel {
    width: min(100%, 520px);
  }

  .entry-scene {
    opacity: 0.12;
  }

  .empty-stage {
    align-items: flex-start;
  }

  .pending-stage {
    grid-template-columns: 1fr;
    align-content: center;
    gap: 12px;
  }

  .journey-visual {
    width: min(88vw, 460px);
    min-height: 230px;
    aspect-ratio: 1.28;
  }

  .pending-copy {
    width: min(100%, 390px);
    margin-inline: auto;
  }

  body[data-stage="response"] .learning-stage {
    grid-template-columns: 1fr;
    height: auto;
    overflow: visible;
  }

  body[data-stage="response"] .reader {
    height: auto;
    max-height: 42vh;
    min-height: 280px;
    padding-bottom: 30px;
    border-bottom: 1px solid var(--line-strong);
  }

  .answer-panel {
    min-height: calc(58vh - var(--appbar-height));
    border-left: 0;
  }

  .answer-scroll {
    overflow: visible;
  }
}

@media (max-width: 640px) {
  :root {
    --appbar-height: 62px;
  }

  body {
    font-size: 15px;
  }

  .auth-view {
    min-height: 100svh;
    padding: 24px 18px 64px;
  }

  .auth-copy h1 {
    font-size: 34px;
  }

  .auth-copy p {
    font-size: 16px;
  }

  .auth-panel {
    gap: 14px;
    padding: 22px 18px;
  }

  .appbar {
    grid-template-columns: 40px minmax(0, 1fr) auto 40px;
    gap: 8px;
    padding: 8px 10px;
  }

  .icon-button {
    width: 40px;
    height: 40px;
  }

  .appbar-meta .connection-dot {
    width: 8px;
    overflow: hidden;
    color: transparent;
  }

  .appbar-meta {
    gap: 6px;
  }

  .lesson-count {
    min-width: 42px;
    font-size: 12px;
  }

  .stage {
    min-height: calc(100svh - var(--appbar-height));
    padding: 30px 18px 54px;
  }

  .stage-heading h2,
  .stage-copy h2 {
    font-size: 30px;
  }

  .empty-stage {
    align-items: center;
  }

  .early-access-panel {
    grid-template-columns: 1fr;
    gap: 16px;
    padding: 18px;
  }

  .early-access-panel .secondary-button {
    width: 100%;
  }

  .learning-period-controls {
    grid-template-columns: minmax(0, 1fr) 88px;
  }

  .learning-map-current,
  .learning-map-goal,
  .learning-map-forecast {
    padding: 15px 16px;
  }

  .wait-note {
    min-height: 142px;
  }

  .wait-note .waiting-primary-copy {
    font-size: 23px;
  }

  .lesson-head {
    display: grid;
    gap: 20px;
  }

  .lesson-heading h2 {
    font-size: 25px;
  }

  .respond-button {
    width: 100%;
  }

  .reader {
    padding: 28px 18px 70px;
  }

  .course-content,
  .opening-story .markdown {
    font-size: 17px;
    line-height: 1.9;
  }

  body[data-stage="response"] .reader {
    max-height: 36svh;
    min-height: 230px;
    padding: 22px 18px;
  }

  body[data-stage="response"] .reader .opening-story,
  body[data-stage="response"] .reader .concept-panel {
    display: none;
  }

  body[data-stage="response"] .lesson-head {
    margin-bottom: 18px;
    padding-bottom: 14px;
  }

  .answer-panel {
    min-height: calc(64svh - var(--appbar-height));
  }

  .answer-scroll {
    padding: 26px 18px 20px;
  }

  .answer-actions {
    position: static;
    padding: 12px 18px calc(12px + env(safe-area-inset-bottom));
  }

  .answer-actions .secondary-button {
    width: 46px;
    padding: 0;
  }

  .answer-actions .secondary-button span {
    display: none;
  }

  .answer-actions .primary-button {
    min-width: 0;
    flex: 1 1 auto;
  }

  .review-next {
    align-items: stretch;
    flex-direction: column;
  }

  .review-next .primary-button {
    width: 100%;
  }

  .expert-roundtable-entry {
    align-items: stretch;
    flex-direction: column;
  }

  .expert-roundtable-entry .secondary-button {
    width: 100%;
  }

  .paywall-actions,
  .dialog-actions {
    flex-direction: column-reverse;
  }

  .paywall-actions button,
  .dialog-actions button {
    width: 100%;
  }

  .drawer-body {
    padding: 20px 16px;
  }

  .account-overview {
    grid-template-columns: 1fr;
  }

  .account-password .primary-button {
    width: 100%;
  }

  .rating-row {
    gap: 5px;
  }

  .rating-row span {
    min-height: 38px;
  }
}

@media (max-width: 360px) {
  html,
  body {
    min-width: 0;
  }

  .pending-stage,
  .review-stage,
  .pending-copy {
    width: 100%;
    min-width: 0;
  }

  .journey-visual {
    width: min(100%, 460px);
    min-width: 0;
  }
}

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

body.reduce-motion *,
body.reduce-motion *::before,
body.reduce-motion *::after {
  scroll-behavior: auto !important;
  animation-duration: 1ms !important;
  animation-iteration-count: 1 !important;
  transition-duration: 1ms !important;
}