/* foundation.css — 基础重置与设计变量 */
:root {
  --brand: #1d4ed8;
  --brand-dark: #1642a8;
  --brand-soft: #eef4ff;
  --ink: #1a1a1a;
  --muted: #5b6472;
  --line: #e5e7eb;
  --bg: #ffffff;
  --bg-soft: #f6f8fb;
  --footer-bg: #0f172a;
  --radius-sm: 8px;
  --radius: 12px;
  --radius-lg: 16px;
  --maxw: 1200px;
  --font: system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
}

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 1rem;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

h1,
h2,
h3,
h4,
p,
figure,
ul,
ol {
  margin: 0;
}

ul,
ol {
  padding: 0;
  list-style: none;
}

h1 {
  font-size: clamp(2rem, 4vw, 3rem);
  line-height: 1.2;
  font-weight: 700;
  letter-spacing: -0.01em;
}

h2 {
  font-size: clamp(1.5rem, 2.4vw, 2rem);
  line-height: 1.3;
  font-weight: 700;
}

h3 {
  font-size: 1.125rem;
  line-height: 1.4;
  font-weight: 600;
}

a {
  color: var(--brand);
  text-decoration: none;
}

a:hover {
  color: var(--brand-dark);
}

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

button {
  font: inherit;
  color: inherit;
  border: 0;
  background: none;
  cursor: pointer;
}

:focus-visible {
  outline: 2px solid var(--brand);
  outline-offset: 3px;
  border-radius: 4px;
}

.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: 20px;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

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

  * {
    transition: none !important;
    animation: none !important;
  }
}