/* =========================================================
   CSS Development Lab 16
   Tooltip / Dropdown Positioning
   ========================================================= */

:root {
  --page-max: 1200px;
  --text: #171717;
  --muted: #686868;
  --line: #e5e5df;
  --surface: #ffffff;
  --soft: #f5f5f1;
  --dark: #171717;
  --radius: 20px;
  --shadow: 0 18px 44px rgba(0, 0, 0, .10);
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--text);
  background: var(--surface);
  font-family: Inter, "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  line-height: 1.65;
}

button {
  font: inherit;
  color: inherit;
}

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

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

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

.eyebrow {
  margin: 0 0 14px;
  color: #858585;
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .15em;
}

.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,
.anchor-copy h2,
.compare h2,
.pitfalls-head h2 {
  margin: 0;
  line-height: 1.04;
  letter-spacing: -.045em;
}

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

.intro-desc {
  max-width: 840px;
  margin: 24px 0 0;
  color: var(--muted);
  font-size: clamp(1rem, 1.7vw, 1.18rem);
}

/* ---------- Main demo ---------- */

.lab {
  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,
.anchor-copy h2,
.compare h2,
.pitfalls-head h2 {
  font-size: clamp(2rem, 4.5vw, 4.5rem);
}

.section-head > p,
.anchor-copy > p,
.compare-grid > div:first-child + *,
.pitfalls-grid p {
  color: var(--muted);
}

.section-head > p {
  margin: 0;
}

.demo-grid {
  margin-top: clamp(38px, 6vw, 60px);
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 18px;
}

.demo-card {
  min-height: 280px;
  padding: 26px;
  border: 1px solid var(--line);
  border-radius: var(--radius);
}

.demo-index {
  color: #999;
  font-size: .78rem;
  font-weight: 800;
}

.demo-card h3 {
  margin: 18px 0 8px;
  font-size: 1.3rem;
}

.demo-card > p {
  margin: 0 0 28px;
  color: var(--muted);
}

.plain-button {
  min-height: 44px;
  padding: 0 16px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  font-weight: 720;
  cursor: pointer;
}

.plain-button img {
  width: 14px;
  height: 14px;
}

/* ---------- Tooltip ---------- */

.tooltip-wrap {
  position: relative;
  display: inline-flex;
}

.tooltip {
  position: absolute;
  left: 50%;
  bottom: calc(100% + 12px);
  z-index: 20;
  width: max-content;
  max-width: min(260px, 80vw);
  padding: 9px 12px;
  border-radius: 9px;
  color: #fff;
  background: #171717;
  box-shadow: var(--shadow);
  font-size: .82rem;
  line-height: 1.4;

  opacity: 0;
  visibility: hidden;
  transform: translate(-50%, 5px);
  pointer-events: none;

  transition:
    opacity 160ms ease,
    transform 160ms ease,
    visibility 160ms;
}

.tooltip::after {
  content: "";
  position: absolute;
  left: 50%;
  top: 100%;
  width: 8px;
  height: 8px;
  background: #171717;
  transform: translate(-50%, -50%) rotate(45deg);
}

.tooltip-wrap:hover .tooltip,
.tooltip-wrap:focus-within .tooltip {
  opacity: 1;
  visibility: visible;
  transform: translate(-50%, 0);
}

.tooltip-bottom {
  top: calc(100% + 12px);
  bottom: auto;
}

.tooltip-bottom::after {
  top: auto;
  bottom: 100%;
  transform: translate(-50%, 50%) rotate(45deg);
}

/* ---------- Dropdown ---------- */

.dropdown-wrap {
  position: relative;
  display: inline-block;
}

.dropdown-trigger[aria-expanded="true"] img {
  transform: rotate(180deg);
}

.dropdown-trigger img {
  transition: transform 180ms ease;
}

.dropdown-menu {
  position: absolute;
  top: calc(100% + 10px);
  left: 0;
  z-index: 30;
  min-width: 190px;
  padding: 8px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  box-shadow: var(--shadow);
}

.dropdown-menu[hidden] {
  display: none;
}

.dropdown-menu a {
  min-height: 40px;
  padding: 0 11px;
  display: flex;
  align-items: center;
  border-radius: 9px;
  color: #444;
  font-size: .9rem;
  font-weight: 650;
}

.dropdown-menu a:hover,
.dropdown-menu a:focus-visible {
  background: var(--soft);
}

.align-demo {
  display: flex;
  justify-content: flex-end;
}

.right-align .dropdown-menu {
  left: auto;
  right: 0;
}

/* ---------- Anchor Positioning progressive enhancement ---------- */

.anchor-section {
  padding: 0 0 clamp(90px, 11vw, 140px);
}

.anchor-grid {
  padding: clamp(30px, 6vw, 64px);
  display: grid;
  grid-template-columns: minmax(0, .9fr) minmax(340px, 1.1fr);
  align-items: center;
  gap: clamp(38px, 7vw, 90px);
  border-radius: 28px;
  background: var(--soft);
}

.anchor-copy > p {
  margin: 22px 0 0;
}

.anchor-demo {
  position: relative;
  min-height: 260px;
  display: grid;
  place-items: center;
  border-radius: 18px;
  background: #fff;
}

.anchor-button {
  min-height: 48px;
  padding: 0 18px;
  border: 0;
  border-radius: 999px;
  color: #fff;
  background: #171717;
  font-weight: 760;
}

.anchor-popover {
  position: absolute;
  left: 50%;
  top: calc(50% + 52px);
  width: min(260px, calc(100% - 30px));
  padding: 16px;
  display: grid;
  gap: 5px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: #fff;
  box-shadow: var(--shadow);
  transform: translateX(-50%);
}

.anchor-popover strong {
  font-size: .92rem;
}

.anchor-popover span {
  color: var(--muted);
  font-size: .84rem;
}

/*
 * Progressive enhancement:
 * 如果浏览器支持 Anchor Positioning，
 * 让浮层直接引用按钮锚点，而不是依赖父级绝对定位。
 */
@supports (anchor-name: --demo-anchor) and (position-anchor: --demo-anchor) {
  .anchor-button {
    anchor-name: --demo-anchor;
  }

  .anchor-popover {
    position: absolute;
    position-anchor: --demo-anchor;

    left: auto;
    top: auto;
    right: auto;
    bottom: auto;

    width: min(260px, calc(100% - 30px));
    position-area: bottom;
    margin-top: 12px;
    transform: none;
  }
}

/* ---------- Compare ---------- */

.compare {
  padding: 0 0 clamp(90px, 11vw, 140px);
}

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

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

.decision-list > div {
  padding: 18px 20px;
  display: grid;
  gap: 4px;
  border-radius: 14px;
  background: var(--soft);
}

.decision-list strong {
  font-size: .94rem;
}

.decision-list span {
  color: var(--muted);
  font-size: .88rem;
}

/* ---------- Pitfalls ---------- */

.pitfalls {
  padding: 0 0 clamp(90px, 12vw, 150px);
}

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

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

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

.pitfalls-grid span {
  color: #999;
  font-size: .78rem;
  font-weight: 800;
}

.pitfalls-grid h3 {
  margin: auto 0 8px;
  font-size: 1.15rem;
}

.pitfalls-grid p {
  margin: 0;
  font-size: .9rem;
}

/* ---------- Responsive ---------- */

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

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

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

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

  .anchor-grid {
    padding: 24px;
  }

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

  .pitfalls-grid article {
    min-height: 180px;
  }
}

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

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition-duration: .01ms !important;
    scroll-behavior: auto !important;
  }
}