:root {
  --primary: #e63946;
  --primary-strong: #9a1f2d;
  --primary-soft: #fce6eb;
  --background: #f1faee;
  --surface: #fffdfb;
  --surface-subtle: #e8f4f8;
  --text: #264653;
  --text-muted: #62717a;
  --divider: rgba(38, 70, 83, 0.18);
  --shadow: rgba(38, 70, 83, 0.1);
  --radius: 12px;
  --max-width: 1120px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --primary-strong: #f0808a;
    --primary-soft: #4a111a;
    --background: #1a1a1a;
    --surface: #262626;
    --surface-subtle: #303636;
    --text: #f8f5f2;
    --text-muted: #d1d5db;
    --divider: rgba(255, 255, 255, 0.16);
    --shadow: rgba(0, 0, 0, 0.28);
    color-scheme: dark;
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--background);
  color: var(--text);
  font-family: "Noto Sans TC", "Noto Sans JP", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
}

a {
  color: inherit;
  text-decoration: none;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: 14px clamp(20px, 5vw, 48px);
  border-bottom: 1px solid var(--divider);
  background: color-mix(in srgb, var(--background) 90%, transparent);
  backdrop-filter: blur(16px);
}

.brand {
  display: inline-flex;
  align-items: baseline;
  gap: 10px;
  min-width: 0;
}

.brand__name {
  font-size: 18px;
  font-weight: 800;
  letter-spacing: 0.04em;
}

.brand__label {
  color: var(--text-muted);
  font-size: 13px;
}

.site-nav a,
.tutorial-index__stage-nav a {
  border-radius: 999px;
  color: var(--text-muted);
  font-size: 14px;
  font-weight: 700;
  padding: 8px 12px;
  transition: background-color 160ms ease, color 160ms ease, transform 160ms ease;
}

.site-nav a:hover,
.tutorial-index__stage-nav a:hover,
.site-nav a:focus-visible,
.tutorial-index__stage-nav a:focus-visible {
  background: var(--primary-soft);
  color: var(--primary-strong);
}

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

h1,
h2,
h3 {
  font-family: "Noto Sans JP", "Noto Sans TC", -apple-system, BlinkMacSystemFont, sans-serif;
  letter-spacing: 0.01em;
}

h1 {
  font-size: clamp(44px, 7vw, 76px);
  line-height: 1.05;
  margin-bottom: 18px;
}

h2 {
  font-size: clamp(30px, 4vw, 44px);
  line-height: 1.15;
  margin-bottom: 0;
}

h3 {
  font-size: clamp(20px, 2.2vw, 26px);
  line-height: 1.3;
  margin-bottom: 10px;
}

.tutorial-index__hero,
.tutorial-index__groups {
  margin: 0 auto;
  max-width: var(--max-width);
  padding-left: clamp(20px, 5vw, 48px);
  padding-right: clamp(20px, 5vw, 48px);
}

.tutorial-index__hero {
  padding-bottom: clamp(48px, 8vw, 88px);
  padding-top: clamp(72px, 11vw, 132px);
}

.tutorial-index__hero > p:not(.tutorial-index__eyebrow) {
  color: var(--text-muted);
  font-size: clamp(18px, 2.2vw, 22px);
  margin-bottom: 28px;
  max-width: 35rem;
}

.tutorial-index__eyebrow,
.tutorial-index__group-heading > p {
  color: var(--primary-strong);
  font-size: 13px;
  font-weight: 800;
  letter-spacing: 0.03em;
  margin-bottom: 10px;
}

.tutorial-index__stage-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tutorial-index__groups {
  padding-bottom: clamp(72px, 11vw, 132px);
}

.tutorial-index__group {
  border-top: 1px solid var(--divider);
  padding: clamp(44px, 7vw, 76px) 0;
  scroll-margin-top: 72px;
}

.tutorial-index__group-heading {
  display: grid;
  gap: 4px;
  margin-bottom: clamp(24px, 4vw, 36px);
}

.tutorial-index__group-heading > p {
  margin-bottom: 0;
}

.tutorial-index__group-heading > span {
  color: var(--text-muted);
  font-size: 16px;
}

.tutorial-index__list {
  display: grid;
  gap: 16px;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.tutorial-index__item {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  min-height: 250px;
  padding: clamp(22px, 3vw, 28px);
  background: var(--surface);
  border: 1px solid var(--divider);
  border-radius: var(--radius);
  box-shadow: 0 10px 24px var(--shadow);
}

.tutorial-index__meta {
  color: var(--primary-strong);
  font-size: 13px;
  font-weight: 800;
  margin-bottom: 12px;
}

.tutorial-index__summary {
  color: var(--text-muted);
  display: -webkit-box;
  margin-bottom: 22px;
  overflow: hidden;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 3;
}

.tutorial-index__link {
  color: var(--primary-strong);
  font-weight: 800;
  margin-top: auto;
  text-decoration: underline;
  text-decoration-thickness: 2px;
  text-underline-offset: 4px;
  transition: color 160ms ease, transform 160ms ease;
}

.tutorial-index__link:hover,
.tutorial-index__link:focus-visible {
  color: var(--primary-strong);
  transform: translateX(2px);
}

a:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 3px;
}

@media (max-width: 680px) {
  .site-header {
    padding-bottom: 12px;
    padding-top: 12px;
  }

  .tutorial-index__list {
    grid-template-columns: 1fr;
  }

  .tutorial-index__item {
    min-height: 0;
  }
}

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

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}