:root {
  --bg: #f3f7fc;
  --bg-strong: #e8eef8;
  --paper: rgba(255, 255, 255, 0.9);
  --paper-strong: #ffffff;
  --ink: #0f172a;
  --muted: #475569;
  --line: #d7e1ee;
  --line-strong: #bfccdc;
  --accent: #1d4ed8;
  --accent-strong: #0f172a;
  --accent-soft: rgba(37, 99, 235, 0.08);
  --accent-soft-2: rgba(15, 23, 42, 0.04);
  --success: #0f766e;
  --shadow: 0 18px 42px rgba(15, 23, 42, 0.08);
  --shadow-sm: 0 10px 24px rgba(15, 23, 42, 0.06);
  --radius-xl: 22px;
  --radius-lg: 18px;
  --radius-md: 12px;
  --radius-sm: 8px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at top left, rgba(59, 130, 246, 0.16), transparent 28%),
    radial-gradient(circle at top right, rgba(15, 23, 42, 0.08), transparent 24%),
    linear-gradient(180deg, #eef4fb 0%, #f8fbff 42%, #f3f7fc 100%);
  font-family: "Inter", "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", sans-serif;
  line-height: 1.8;
  padding-top: 92px;
}

a {
  color: inherit;
}

code {
  padding: 3px 7px;
  border-radius: 7px;
  border: 1px solid rgba(37, 99, 235, 0.14);
  background: rgba(255, 255, 255, 0.82);
  color: #1e3a8a;
  font-family: "JetBrains Mono", "Consolas", "Courier New", monospace;
  font-size: 0.94em;
}

.wrap {
  width: min(1180px, calc(100vw - 32px));
  margin: 0 auto;
}

.site-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 50;
  border-bottom: 1px solid rgba(148, 163, 184, 0.18);
  background: rgba(248, 251, 255, 0.84);
  backdrop-filter: blur(18px);
  box-shadow: 0 6px 22px rgba(15, 23, 42, 0.04);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 16px 0;
}

.brand {
  font-weight: 800;
  letter-spacing: -0.02em;
  text-decoration: none;
  white-space: nowrap;
}

.nav {
  display: flex;
  flex-wrap: nowrap;
  gap: 12px;
  overflow-x: auto;
  scrollbar-width: none;
}

.nav::-webkit-scrollbar {
  display: none;
}

.nav a {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  padding: 10px 14px;
  border: 1px solid rgba(148, 163, 184, 0.24);
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.74);
  color: var(--muted);
  text-decoration: none;
  font-weight: 600;
  white-space: nowrap;
  transition: background-color 0.18s ease-out, border-color 0.18s ease-out, color 0.18s ease-out, transform 0.18s ease-out;
}

.nav a:hover,
.nav a:focus-visible {
  background: var(--paper-strong);
  border-color: rgba(37, 99, 235, 0.24);
  color: var(--accent-strong);
  outline: none;
  transform: translateY(-1px);
}

.hero {
  padding: 22px 0 32px;
}

.hero-grid,
.two-col,
.footer-grid,
.plan-grid,
.project-grid {
  display: grid;
  grid-template-columns: 1.18fr 0.82fr;
  gap: 24px;
}

.eyebrow,
.section-label {
  display: inline-flex;
  align-items: center;
  margin: 0 0 12px;
  padding: 6px 12px;
  border-radius: 999px;
  border: 1px solid rgba(37, 99, 235, 0.12);
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  margin: 0;
  line-height: 1.15;
  letter-spacing: -0.02em;
}

h1 {
  margin-top: 12px;
  font-size: clamp(38px, 5vw, 64px);
}

h2 {
  font-size: clamp(28px, 3vw, 40px);
}

h3 {
  font-size: 22px;
}

.lead,
.section-text,
.intro,
.muted {
  color: var(--muted);
}

.lead {
  max-width: 65ch;
  font-size: 18px;
}

.hero-actions,
.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 24px;
}

.button {
  min-height: 46px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 12px 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--paper-strong);
  color: var(--ink);
  text-decoration: none;
  font-weight: 700;
  transition: transform 0.16s ease-out, box-shadow 0.16s ease-out, border-color 0.16s ease-out, background-color 0.16s ease-out;
}

.button:hover,
.button:focus-visible {
  border-color: rgba(37, 99, 235, 0.24);
  box-shadow: 0 10px 20px rgba(37, 99, 235, 0.08);
  transform: translateY(-1px);
  outline: none;
}

.button.primary {
  border-color: #1d4ed8;
  background: linear-gradient(135deg, #1d4ed8, #2563eb);
  color: #fff;
}

.main-stack {
  padding: 12px 0 64px;
}

.section {
  margin-top: 34px;
}

section[id] {
  scroll-margin-top: 110px;
}

.section-head {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 20px;
  margin-bottom: 18px;
}

.section-head > * {
  flex: 1;
}

.panel,
.path-card,
.unit-card,
.roadmap a,
.note,
.lesson-card,
.project-card,
.rubric,
.summary-box {
  background:
    linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(248, 251, 255, 0.9));
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}

.panel,
.lesson-card,
.project-card,
.rubric,
.summary-box {
  padding: 26px;
}

.callout {
  align-self: start;
  position: relative;
  overflow: hidden;
}

.callout::before,
.summary-box::before {
  content: "";
  position: absolute;
  inset: 0 auto auto 0;
  width: 100%;
  height: 4px;
  background: linear-gradient(90deg, #1d4ed8, #60a5fa);
}

.hero-visual,
.figure-card {
  overflow: hidden;
}

.hero-visual img,
.figure-card img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 14px;
}

.figure-card p {
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 15px;
}

.clean-list {
  margin: 14px 0 0;
  padding-left: 20px;
}

.clean-list li + li {
  margin-top: 8px;
}

.path-grid,
.unit-grid {
  display: grid;
  gap: 18px;
}

.path-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

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

.path-card,
.unit-card,
.roadmap a {
  padding: 22px;
  text-decoration: none;
  transition: transform 0.18s ease-out, border-color 0.18s ease-out, box-shadow 0.18s ease-out;
}

.path-card:hover,
.unit-card:hover,
.roadmap a:hover,
.path-card:focus-within,
.unit-card:focus-visible,
.roadmap a:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(37, 99, 235, 0.22);
  box-shadow: 0 14px 28px rgba(15, 23, 42, 0.08);
  outline: none;
}

.path-card span,
.unit-card strong {
  color: var(--accent);
}

.roadmap {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 16px;
}

.roadmap a {
  font-weight: 700;
}

.site-footer {
  padding: 18px 0 42px;
  color: var(--muted);
}

.footer-grid {
  grid-template-columns: 1fr 1fr;
}

.page-hero {
  padding: 28px 0 14px;
}

.breadcrumb {
  margin-bottom: 10px;
  color: var(--muted);
  font-size: 14px;
}

.content-grid {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 24px;
  padding: 18px 0 60px;
}

.sidebar {
  position: sticky;
  top: 112px;
  align-self: start;
  padding: 20px;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(245, 249, 255, 0.92));
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}

.sidebar h3 {
  font-size: 18px;
  margin-bottom: 10px;
}

.sidebar a {
  display: block;
  padding: 9px 0;
  color: var(--muted);
  text-decoration: none;
}

.sidebar a:hover,
.sidebar a:focus-visible {
  color: var(--accent-strong);
  outline: none;
}

.article {
  display: grid;
  gap: 18px;
}

.figure-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.article section {
  padding: 28px;
}

.article p,
.article li {
  margin-top: 10px;
}

.tag-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 16px;
}

.tag {
  display: inline-flex;
  align-items: center;
  padding: 6px 12px;
  border-radius: 999px;
  border: 1px solid rgba(37, 99, 235, 0.14);
  background: rgba(255, 255, 255, 0.8);
  color: var(--accent);
  font-weight: 700;
  font-size: 14px;
}

.lesson-card + .lesson-card,
.project-card + .project-card {
  margin-top: 16px;
}

.mini-title {
  margin-top: 0;
  font-size: 18px;
}

.rubric table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 12px;
}

.rubric th,
.rubric td {
  padding: 12px;
  border-top: 1px solid var(--line);
  text-align: left;
  vertical-align: top;
}

.summary-box {
  position: relative;
  overflow: hidden;
  background:
    linear-gradient(135deg, rgba(37, 99, 235, 0.08), rgba(255, 255, 255, 0) 34%),
    linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(244, 248, 255, 0.94));
}

@media (max-width: 980px) {
  body {
    padding-top: 118px;
  }

  .hero-grid,
  .two-col,
  .footer-grid,
  .path-grid,
  .roadmap,
  .content-grid,
  .plan-grid,
  .project-grid,
  .unit-grid,
  .figure-grid {
    grid-template-columns: 1fr;
  }

  .section-head,
  .topbar {
    display: block;
  }

  .nav {
    margin-top: 12px;
    padding-bottom: 2px;
  }

  .sidebar {
    position: static;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    transition: none !important;
    animation: none !important;
  }
}