:root {
  --bg: #f5f5f7;
  --bg-soft: #fbfbfd;
  --surface: rgba(255, 255, 255, 0.78);
  --surface-strong: rgba(255, 255, 255, 0.94);
  --surface-muted: rgba(255, 255, 255, 0.62);
  --ink: #101114;
  --muted: #6e6e73;
  --line: rgba(15, 23, 42, 0.08);
  --line-strong: rgba(15, 23, 42, 0.14);
  --brand: #0a84ff;
  --brand-deep: #0066cc;
  --brand-soft: rgba(10, 132, 255, 0.1);
  --accent: #111111;
  --success: #1f8f52;
  --danger: #c63b16;
  --shadow-soft: 0 16px 40px rgba(15, 23, 42, 0.05);
  --shadow-strong: 0 28px 80px rgba(15, 23, 42, 0.08);
  --radius-2xl: 36px;
  --radius-xl: 28px;
  --radius-lg: 22px;
  --radius-md: 16px;
  --radius-sm: 12px;
  --page-width: 1380px;
  --content-width: 1220px;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0; min-height: 100vh; overflow-x: hidden; overflow-y: auto;
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "Helvetica Neue", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(10, 132, 255, 0.14), transparent 28%),
    radial-gradient(circle at 80% 0%, rgba(255, 255, 255, 0.92), transparent 30%),
    linear-gradient(180deg, #fcfcfe 0%, #f1f2f6 44%, #f6f6f8 100%);
}
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }
button, input, select, textarea { font: inherit; }
.page-shell { max-width: var(--page-width); margin: 0 auto; padding: 18px 18px 80px; }
.page-nav {
  position: sticky; top: 14px; z-index: 40;
  display: flex; align-items: center; justify-content: space-between; gap: 20px;
  max-width: var(--content-width); margin: 0 auto; padding: 14px 18px;
  border-radius: 999px; background: rgba(255, 255, 255, 0.8);
  border: 1px solid rgba(255, 255, 255, 0.54);
  box-shadow: 0 18px 60px rgba(15, 23, 42, 0.08); backdrop-filter: blur(20px);
}
.nav-brand, .hero-eyebrow {
  display: inline-flex; align-items: center; gap: 14px;
  font-weight: 600; letter-spacing: -0.02em; line-height: 1.2;
}
.nav-brand img, .hero-eyebrow img { width: 34px; height: 34px; border-radius: 11px; flex-shrink: 0; align-self: center; }
.nav-brand span, .hero-eyebrow span { display: block; }
.hero-eyebrow {
  width: fit-content; padding: 12px 16px; border-radius: 999px;
  background: rgba(255, 255, 255, 0.58); border: 1px solid rgba(15, 23, 42, 0.06);
  box-shadow: 0 12px 24px rgba(15, 23, 42, 0.04);
}
.nav-links, .hero-links, .hero-actions, .panel-actions, .badge-row,
.quiz-controls, .stats-grid { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; }
.nav-links { gap: 6px; }
.nav-links a {
  border-radius: 999px; padding: 10px 14px; color: var(--muted);
  transition: background-color 0.18s ease, color 0.18s ease;
}
.nav-links a:hover, .nav-links a[aria-current="page"] {
  background: rgba(15, 23, 42, 0.06); color: var(--ink);
}
.hero, .panel, .feature-card, .question-card, .knowledge-card,
.reader-card, .quiz-shell, .empty-state, .source-item, .stage-card {
  background: var(--surface); border: 1px solid rgba(255, 255, 255, 0.46);
  box-shadow: var(--shadow-soft); backdrop-filter: blur(18px);
  animation: rise-in 0.55s ease both;
}
@keyframes rise-in { from { opacity: 0; transform: translateY(20px); } to { opacity: 1; transform: translateY(0); } }
.hero {
  max-width: var(--content-width); margin: 24px auto 0; padding: 42px;
  border-radius: 40px; position: relative; overflow: hidden;
}
.hero::before {
  content: ""; position: absolute; inset: auto auto -24% -10%;
  width: 320px; height: 320px; border-radius: 50%;
  background: radial-gradient(circle, rgba(10, 132, 255, 0.16), transparent 68%); pointer-events: none;
}
.hero::after {
  content: ""; position: absolute; inset: 10% -5% auto auto;
  width: 220px; height: 220px; border-radius: 50%;
  background: radial-gradient(circle, rgba(255, 255, 255, 0.78), transparent 72%); pointer-events: none;
}
.hero-inner, .hero-grid, .hero-home-copy, .hero-home-aside { position: relative; z-index: 1; }
.hero-grid { display: grid; grid-template-columns: 1fr; gap: 28px; align-items: end; justify-items: center; text-align: center; }
.hero-home-copy, .hero-home-aside { display: flex; flex-direction: column; }
.hero-home-copy { align-items: center; width: 100%; }
.hero-home-aside { width: min(100%, 1080px); margin-top: 8px; }
.hero-kpi-grid { display: grid; gap: 14px; grid-template-columns: repeat(3, minmax(0, 1fr)); }
.hero h1 { margin: 14px 0 18px; font-size: clamp(2.8rem, 5.6vw, 5rem); line-height: 0.9; letter-spacing: -0.065em; font-weight: 700; }
.hero-copy { max-width: 760px; margin: 0 auto; font-size: 1.08rem; line-height: 1.72; color: var(--muted); }
.hero-note { max-width: 820px; margin: 18px auto 0; padding: 16px 18px; border-radius: 20px; background: rgba(15, 23, 42, 0.04); color: var(--muted); line-height: 1.6; text-align: center; }
.hero-actions { margin-top: 32px; column-gap: 16px; row-gap: 14px; justify-content: center; }
.hero-kpi, .source-item, .stage-card { border-radius: 24px; padding: 22px; display: flex; flex-direction: column; min-height: 100%; }
.hero-kpi h3, .source-item h3, .stage-card h3, .feature-card h3,
.panel h2, .section-title h2, .reader-card h3, .knowledge-card h3,
.question-card h3, .quiz-shell h3 { margin: 0 0 10px; letter-spacing: -0.03em; }
.hero-kpi .value { display: block; margin-bottom: 10px; font-size: 2rem; font-weight: 700; letter-spacing: -0.05em; }
.hero-kpi .label { display: inline-block; margin-bottom: 8px; color: var(--brand-deep); font-size: 0.88rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.08em; }
.panel-subtitle, .muted { color: var(--muted); }
.button {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  min-height: 48px; padding: 12px 22px; border-radius: 999px;
  border: 1px solid transparent; cursor: pointer; line-height: 1.1; white-space: nowrap;
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease, background-color 0.18s ease;
}
.button:hover { transform: translateY(-1px); }
.button:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }
.button-primary { background: linear-gradient(180deg, #0a84ff, #0071e3); color: #ffffff; box-shadow: 0 18px 30px rgba(10, 132, 255, 0.22); }
.button-secondary { background: rgba(255, 255, 255, 0.74); color: var(--ink); border-color: rgba(15, 23, 42, 0.08); }
.button-tertiary { background: transparent; color: var(--brand-deep); border-color: rgba(10, 132, 255, 0.18); }
.button-danger { background: rgba(198, 59, 22, 0.08); color: var(--danger); border-color: rgba(198, 59, 22, 0.16); }
.feature-grid, .source-grid, .page-switch-grid, .guide-strip,
.knowledge-list, .question-list, .reader-list, .content-stack { display: grid; gap: 22px; }
.feature-grid, .page-switch-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); max-width: var(--content-width); width: 100%; margin: 24px auto 0; }
.source-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); max-width: var(--content-width); width: 100%; margin: 24px auto 0; }
.guide-strip { grid-template-columns: repeat(5, minmax(0, 1fr)); margin-top: 20px; }
.feature-card { border-radius: 26px; padding: 28px; display: flex; flex-direction: column; min-height: 100%; }
.feature-card p { margin: 0; }
.section-panel, .panel { border-radius: var(--radius-2xl); padding: 26px; }
.section-panel { max-width: var(--content-width); width: 100%; margin: 24px auto 0; }
.home-section { padding: 0; }
.home-section .section-title { padding: 4px 2px 0; }
.home-section .page-switch-grid, .home-section .source-grid { max-width: none; margin-top: 18px; }
.section-title, .panel-title, .question-header, .quiz-headline, .practice-title-row {
  display: flex; justify-content: space-between; align-items: flex-start; gap: 14px;
}
.section-title-stack { align-items: center; }
.panel-actions { margin-top: 20px; column-gap: 14px; row-gap: 14px; }
.workspace-guide .button { width: 100%; }
.workspace-switch.active { background: linear-gradient(180deg, #0a84ff, #0071e3); color: #ffffff; border-color: transparent; box-shadow: 0 18px 30px rgba(10, 132, 255, 0.22); }
.stats-grid { margin-top: 26px; }
.stats-grid-wide { justify-content: center; }
.stat-tile {
  min-width: 150px; flex: 1 1 150px; max-width: 180px;
  padding: 20px 18px; border-radius: 22px;
  background: rgba(255, 255, 255, 0.6); border: 1px solid rgba(15, 23, 42, 0.06);
}
.stat-tile .value { display: block; font-size: 1.92rem; font-weight: 700; letter-spacing: -0.06em; }
.stat-tile .label { display: block; margin-top: 6px; color: var(--muted); font-size: 0.93rem; }
.workspace-shell { display: grid; grid-template-columns: 320px minmax(0, 1fr); gap: 24px; max-width: var(--content-width); margin: 24px auto 0; }
.workspace-sidebar { display: grid; gap: 18px; align-self: start; position: sticky; top: 92px; }
.workspace-main, .reader-main { display: grid; gap: 22px; }
.field { display: grid; gap: 8px; }
.field + .field { margin-top: 16px; }
.field label { font-size: 0.94rem; font-weight: 600; }
.text-input, .select-input, .number-input, .textarea-input {
  width: 100%; padding: 14px 15px; border-radius: 16px;
  border: 1px solid rgba(15, 23, 42, 0.08); background: rgba(255, 255, 255, 0.92); color: var(--ink);
}
.text-input:focus, .select-input:focus, .number-input:focus, .textarea-input:focus { outline: none; border-color: rgba(10, 132, 255, 0.3); box-shadow: 0 0 0 4px rgba(10, 132, 255, 0.08); }
.chip-group, .badge-row { display: flex; flex-wrap: wrap; gap: 10px; }
.chip, .tag, .status-pill {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  border-radius: 999px; padding: 8px 12px;
  border: 1px solid rgba(15, 23, 42, 0.08); background: rgba(255, 255, 255, 0.7);
  color: var(--muted); font-size: 0.9rem;
}
.chip { cursor: pointer; }
.chip-count { display: inline-flex; align-items: center; justify-content: center; min-width: 22px; min-height: 22px; padding: 0 6px; border-radius: 999px; background: rgba(15, 23, 42, 0.06); font-size: 0.82rem; line-height: 1; }
.chip.active, .tree-item.active { background: rgba(10, 132, 255, 0.1); border-color: rgba(10, 132, 255, 0.18); color: var(--brand-deep); }
.tag-brand { background: rgba(10, 132, 255, 0.1); color: var(--brand-deep); border-color: rgba(10, 132, 255, 0.14); }
.tag-accent { background: rgba(15, 23, 42, 0.05); color: var(--ink); }
.tag-dark { background: rgba(110, 110, 115, 0.08); color: var(--muted); }
.tag-origin { background: rgba(86, 90, 255, 0.08); color: #4a43c5; border-color: rgba(86, 90, 255, 0.12); }
.knowledge-list-wide { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.knowledge-card, .question-card, .reader-card, .quiz-shell { border-radius: 28px; padding: 24px; }
.knowledge-card, .question-card, .tree-item, .source-item, .stage-card { transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease; }
.knowledge-card:hover, .question-card:hover, .tree-item:hover, .source-item:hover, .stage-card:hover { transform: translateY(-2px); border-color: var(--line-strong); box-shadow: var(--shadow-strong); }
.knowledge-card.active { border-color: rgba(10, 132, 255, 0.18); box-shadow: 0 20px 48px rgba(10, 132, 255, 0.08); }
.tabbed-panel.hidden { display: none; }
.question-list { grid-template-columns: 1fr; }
.question-title { margin: 0; font-size: 1.18rem; line-height: 1.65; }
.question-options, .answer-options { display: grid; gap: 12px; margin-top: 14px; }
.answer-options-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.option, .answer-option { padding: 14px 16px; border-radius: 18px; border: 1px solid rgba(15, 23, 42, 0.08); background: rgba(255, 255, 255, 0.84); }
.answer-option { display: grid; grid-template-columns: auto auto 1fr; align-items: start; gap: 12px; cursor: pointer; transition: border-color 0.18s ease, box-shadow 0.18s ease, background-color 0.18s ease; }
.answer-option input { margin-top: 5px; }
.answer-option:hover { border-color: rgba(10, 132, 255, 0.2); background: rgba(255, 255, 255, 0.92); }
.answer-option:has(input:checked) { border-color: rgba(10, 132, 255, 0.24); background: rgba(10, 132, 255, 0.08); box-shadow: 0 12px 24px rgba(10, 132, 255, 0.08); }
.answer-option-key { display: inline-flex; align-items: center; justify-content: center; min-width: 28px; min-height: 28px; padding: 0 8px; border-radius: 999px; background: rgba(15, 23, 42, 0.06); color: var(--ink); font-size: 0.86rem; font-weight: 700; line-height: 1; }
.answer-option-text { display: block; line-height: 1.55; }
.practice-shell, .analysis-box, .quiz-result, .callout, .reader-summary, .practice-feedback { border-radius: 20px; border: 1px solid rgba(15, 23, 42, 0.07); background: rgba(255, 255, 255, 0.74); padding: 18px; }
.question-card, .practice-shell, .analysis-box, .quiz-result, .reader-card { display: grid; gap: 16px; }
.question-card .panel-actions { margin-top: 6px; }
.callout { background: linear-gradient(180deg, rgba(10, 132, 255, 0.08), rgba(255, 255, 255, 0.82)); }
.practice-feedback.correct { border-color: rgba(31, 143, 82, 0.14); background: rgba(31, 143, 82, 0.08); }
.practice-feedback.wrong { border-color: rgba(198, 59, 22, 0.16); background: rgba(198, 59, 22, 0.08); }
.analysis-box.hidden, .quiz-shell.hidden { display: none; }
.progress-bar { width: 100%; height: 10px; border-radius: 999px; overflow: hidden; background: rgba(15, 23, 42, 0.08); }
.progress-value { height: 100%; background: linear-gradient(90deg, #0a84ff, #54a6ff); }
.score-badge { padding: 10px 14px; border-radius: 999px; background: rgba(10, 132, 255, 0.1); color: var(--brand-deep); font-weight: 600; }
.reader-layout { display: grid; grid-template-columns: 320px minmax(0, 1fr); gap: 24px; max-width: var(--content-width); margin: 24px auto 0; }
.reader-sidebar { display: grid; gap: 18px; align-self: start; position: sticky; top: 92px; }
.tree-list { display: grid; gap: 10px; max-height: 400px; overflow-y: auto; }
.tree-item { text-align: left; padding: 15px 16px; border-radius: 18px; border: 1px solid rgba(15, 23, 42, 0.08); background: rgba(255, 255, 255, 0.8); cursor: pointer; }
.tree-item strong, .question-card strong, .reader-card strong { letter-spacing: -0.02em; }
.empty-state { border-radius: 28px; padding: 54px 28px; text-align: center; }
.footer-note { max-width: var(--content-width); margin: 26px auto 0; text-align: center; color: var(--muted); font-size: 0.95rem; }
.code { font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace; }

@media (max-width: 1100px) {
  .hero-grid, .feature-grid, .source-grid, .page-switch-grid, .guide-strip,
  .knowledge-list-wide, .workspace-shell, .reader-layout, .hero-kpi-grid { grid-template-columns: 1fr; }
  .page-nav, .workspace-sidebar, .reader-sidebar { position: static; }
}
@media (max-width: 760px) {
  .page-shell { padding: 14px 12px 56px; }
  .page-nav, .hero, .section-panel, .panel, .feature-card, .question-card,
  .knowledge-card, .reader-card, .quiz-shell, .source-item, .stage-card { padding: 18px; }
  .hero h1 { font-size: 2.9rem; }
  .page-nav, .section-title, .panel-title, .quiz-headline, .question-header, .practice-title-row { flex-direction: column; align-items: flex-start; }
  .answer-options-grid { grid-template-columns: 1fr; }
}