/* =========================================================
   CSS Development Lab 19
   Cascade + @layer
   ========================================================= */

/*
 * 先声明 Layer 顺序。
 * 对普通声明而言，越靠后的 Layer 优先级越高。
 */
@layer reset, base, components, utilities;

/* =========================================================
   1. RESET
   ========================================================= */

@layer reset {
  *,
  *::before,
  *::after {
    box-sizing: border-box;
  }

  body,
  h1,
  h2,
  h3,
  p,
  pre {
    margin: 0;
  }

  img {
    display: block;
    max-width: 100%;
  }

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

/* =========================================================
   2. BASE
   ========================================================= */

@layer base {
  :root {
    --page-max: 1200px;
    --text: #171717;
    --muted: #686868;
    --line: #e5e5df;
    --surface: #ffffff;
    --soft: #f5f5f1;
    --dark: #171717;
    --radius: 20px;
  }

  html {
    scroll-behavior: smooth;
  }

  body {
    color: var(--text);
    background: var(--surface);
    font-family: Inter, "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
    line-height: 1.65;
  }

  code,
  pre {
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  }

  .page-wrap {
    width: min(calc(100% - 40px), var(--page-max));
    margin-inline: auto;
  }

  .eyebrow {
    margin-bottom: 14px;
    color: #858585;
    font-size: .78rem;
    font-weight: 800;
    letter-spacing: .15em;
  }

  :focus-visible {
    outline: 2px solid #171717;
    outline-offset: 3px;
  }
}

/* =========================================================
   3. COMPONENTS
   ========================================================= */

@layer components {
  .intro {
    padding: clamp(72px, 10vw, 130px) 0 clamp(58px, 8vw, 90px);
    background:
      radial-gradient(circle at 86% 14%, rgba(0,0,0,.05), transparent 27%),
      linear-gradient(180deg, #fafaf8 0%, #f3f3ef 100%);
  }

  .intro-inner {
    max-width: 1000px;
  }

  .intro h1,
  .section-head h2,
  .layer-copy h2,
  .specificity h2,
  .architecture-head h2,
  .warning h2 {
    line-height: 1.04;
    letter-spacing: -.045em;
  }

  .intro h1 {
    font-size: clamp(2.8rem, 7vw, 6rem);
  }

  .intro-desc {
    max-width: 840px;
    margin-top: 24px;
    color: var(--muted);
    font-size: clamp(1rem, 1.7vw, 1.18rem);
  }

  .lab,
  .button-demo {
    padding: clamp(80px, 10vw, 130px) 0;
  }

  .section-head {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(280px, .78fr);
    align-items: end;
    gap: clamp(28px, 6vw, 80px);
  }

  .section-head h2,
  .layer-copy h2,
  .specificity h2,
  .architecture-head h2,
  .warning h2 {
    font-size: clamp(2rem, 4.5vw, 4.5rem);
  }

  .section-head > p,
  .layer-copy > p,
  .specificity-grid > div:first-child > p:last-child {
    color: var(--muted);
  }

  .problem-grid {
    margin-top: clamp(38px, 6vw, 60px);
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    gap: 16px;
  }

  .problem-card {
    min-width: 0;
    min-height: 300px;
    padding: 24px;
    display: flex;
    flex-direction: column;
    border: 1px solid var(--line);
    border-radius: var(--radius);
  }

  .problem-card > span {
    color: #999;
    font-size: .78rem;
    font-weight: 800;
  }

  .problem-card h3 {
    margin-top: 22px;
    font-size: 1.25rem;
  }

  .problem-card p {
    margin-top: 9px;
    color: var(--muted);
    font-size: .92rem;
  }

  .problem-card pre {
    margin-top: auto;
    padding: 16px;
    overflow-x: auto;
    border-radius: 12px;
    color: #f2f2f2;
    background: #181818;
    font-size: .78rem;
    line-height: 1.6;
  }

  /* ---------- Layer demo ---------- */

  .layer-demo {
    padding-bottom: clamp(90px, 11vw, 140px);
  }

  .layer-grid {
    padding: clamp(30px, 6vw, 64px);
    display: grid;
    grid-template-columns: minmax(0, .85fr) minmax(320px, 1.15fr);
    align-items: center;
    gap: clamp(36px, 7vw, 90px);
    border-radius: 28px;
    background: var(--soft);
  }

  .layer-copy > p {
    margin-top: 22px;
  }

  .layer-stack {
    display: grid;
    gap: 10px;
  }

  .layer-item {
    min-height: 74px;
    padding: 14px 18px;
    display: grid;
    grid-template-columns: 36px 120px minmax(0, 1fr);
    align-items: center;
    gap: 12px;
    border: 1px solid var(--line);
    border-radius: 13px;
    background: #fff;
  }

  .layer-item span {
    color: #999;
    font-size: .76rem;
    font-weight: 800;
  }

  .layer-item strong {
    font-size: .94rem;
  }

  .layer-item small {
    color: var(--muted);
  }

  /* ---------- Practical buttons ---------- */

  .button-row {
    margin-top: 40px;
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
  }

  .button {
    min-height: 46px;
    padding: 0 18px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--dark);
    border-radius: 999px;
    color: #fff;
    background: var(--dark);
    font-size: .9rem;
    font-weight: 760;
  }

  .code-card {
    margin-top: 34px;
    min-width: 0;
    overflow-x: auto;
    border-radius: 18px;
    background: #181818;
  }

  .code-card pre {
    padding: clamp(22px, 4vw, 34px);
  }

  .code-card code {
    color: #f2f2f2;
    font-size: clamp(.8rem, 1.4vw, .94rem);
    line-height: 1.75;
  }

  /* ---------- Specificity ---------- */

  .specificity {
    padding-bottom: clamp(90px, 11vw, 140px);
  }

  .specificity-grid {
    display: grid;
    grid-template-columns: minmax(0, .85fr) minmax(320px, 1.15fr);
    align-items: center;
    gap: clamp(36px, 7vw, 90px);
  }

  .specificity-grid > div:first-child > p:last-child {
    margin-top: 22px;
  }

  .score-list {
    display: grid;
    border-top: 1px solid var(--line);
  }

  .score-list > div {
    padding: 16px 0;
    display: grid;
    grid-template-columns: 120px minmax(0, 1fr) 58px;
    gap: 14px;
    border-bottom: 1px solid var(--line);
  }

  .score-list code {
    font-weight: 750;
  }

  .score-list span {
    color: var(--muted);
  }

  .score-list strong {
    text-align: right;
    font-size: .84rem;
  }

  /* ---------- Architecture ---------- */

  .architecture {
    padding-bottom: clamp(90px, 11vw, 140px);
  }

  .architecture-head {
    max-width: 780px;
  }

  .architecture-grid {
    margin-top: 38px;
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 16px;
  }

  .architecture-grid article {
    min-height: 220px;
    padding: 24px;
    display: flex;
    flex-direction: column;
    border: 1px solid var(--line);
    border-radius: 18px;
  }

  .architecture-grid span {
    align-self: flex-start;
    padding: 5px 9px;
    border-radius: 999px;
    background: var(--soft);
    font-size: .74rem;
    font-weight: 800;
  }

  .architecture-grid h3 {
    margin-top: auto;
    font-size: 1.12rem;
  }

  .architecture-grid p {
    margin-top: 8px;
    color: var(--muted);
    font-size: .9rem;
  }

  /* ---------- Warning ---------- */

  .warning {
    padding-bottom: clamp(90px, 12vw, 150px);
  }

  .warning-grid {
    padding: clamp(30px, 6vw, 64px);
    display: grid;
    grid-template-columns: minmax(0, .8fr) minmax(360px, 1.2fr);
    align-items: center;
    gap: clamp(36px, 7vw, 90px);
    border-radius: 28px;
    background: var(--soft);
  }

  .warning-list {
    display: grid;
    gap: 12px;
  }

  .warning-list p {
    padding: 16px 18px;
    border-radius: 12px;
    background: #fff;
    color: var(--muted);
  }

  .warning-list strong {
    color: var(--text);
  }

  @media (max-width: 900px) {
    .section-head,
    .layer-grid,
    .specificity-grid,
    .warning-grid {
      grid-template-columns: 1fr;
    }

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

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

  @media (max-width: 680px) {
    .page-wrap {
      width: calc(100% - 28px);
    }

    .layer-grid,
    .warning-grid {
      padding: 24px;
    }

    .layer-item {
      grid-template-columns: 30px 100px minmax(0, 1fr);
    }

    .layer-item small {
      font-size: .78rem;
    }

    .button-row {
      display: grid;
    }

    .button {
      width: 100%;
    }

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

    .score-list > div {
      grid-template-columns: 92px minmax(0, 1fr) 48px;
    }
  }
}

/* =========================================================
   4. UTILITIES
   ========================================================= */

@layer utilities {
  /*
   * 这些类选择器并不比 .button 更“具体”，
   * 但 utilities Layer 在 components 之后，
   * 所以普通声明可以自然覆盖组件层。
   */

  .u-quiet {
    border-color: var(--line);
    color: var(--text);
    background: var(--soft);
  }

  .u-wide {
    padding-inline: 34px;
  }
}

/* =========================================================
   Important note
   ========================================================= */

/*
 * 未放入 Layer 的普通声明会优先于 Layer 内的普通声明。
 * 所以大型项目一旦决定使用 @layer，建议建立清晰规则，
 * 不要随意在 Layer 外继续堆普通组件覆盖样式。
 */

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