/* ==========================================================================
   base.css — 重置、排版基线、布局原语
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 24px);
  background: var(--bg-base);
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  background: var(--bg-base);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: var(--fs-16);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: "tnum" 0;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.015em;
  color: var(--text-primary);
}

p { margin: 0; }

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--dur) var(--ease);
}

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

ul, ol { margin: 0; padding: 0; }

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

input, select, textarea { font: inherit; color: inherit; }

hr {
  border: none;
  border-top: 1px solid var(--border-light);
  margin: var(--sp-12) 0;
}

::selection { background: var(--brand-20); color: var(--text-primary); }

:focus-visible {
  outline: 2px solid var(--border-focus);
  outline-offset: 2px;
  border-radius: var(--r-sm);
}

/* --- 滚动条 --- */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
  background: var(--border-medium);
  border-radius: var(--r-pill);
  border: 3px solid var(--bg-base);
}
::-webkit-scrollbar-thumb:hover { background: var(--border-strong); }

/* ==========================================================================
   布局原语
   ========================================================================== */

.wrap {
  width: 100%;
  max-width: var(--page-max);
  margin-inline: auto;
  padding-inline: var(--sp-6);
}

.section { padding-block: var(--sp-24); }
.section--tight { padding-block: var(--sp-16); }

.stack > * + * { margin-top: var(--sp-4); }

.grid { display: grid; gap: var(--sp-4); }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }

.row { display: flex; align-items: center; gap: var(--sp-3); }
.row--between { justify-content: space-between; }
.row--wrap { flex-wrap: wrap; }

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

/* ==========================================================================
   排版工具
   ========================================================================== */

/* 英文小标签开场 — 参考站签名手法之一 */
.eyebrow {
  display: block;
  font-family: "Instrument Sans", var(--font-cn);
  font-size: var(--fs-12);
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-tertiary);
  margin-bottom: var(--sp-4);
}

.eyebrow--accent { color: var(--text-accent); }

/* 衬线斜体强调 — 嵌在中文标题里 */
.it {
  font-family: var(--font-serif);
  font-style: italic;
  font-weight: 400;
  letter-spacing: 0;
}

.display-1 { font-size: clamp(38px, 6.4vw, 72px); line-height: 1.1; }
.display-2 { font-size: clamp(30px, 4.6vw, 52px); line-height: 1.14; }
.display-3 { font-size: clamp(24px, 3.2vw, 36px); line-height: 1.2; }

.t-lead {
  font-size: var(--fs-18);
  line-height: 1.75;
  color: var(--text-secondary);
}

.t-sec  { color: var(--text-secondary); }
.t-ter  { color: var(--text-tertiary); }
.t-acc  { color: var(--text-accent); }
.t-sm   { font-size: var(--fs-14); }
.t-xs   { font-size: var(--fs-13); }
.t-num  { font-family: "Instrument Sans", var(--font-cn); font-feature-settings: "tnum"; }
.t-mono { font-family: var(--font-mono); font-size: 0.92em; }

.mt-0 { margin-top: 0 !important; }
.mt-2 { margin-top: var(--sp-2); }
.mt-3 { margin-top: var(--sp-3); }
.mt-4 { margin-top: var(--sp-4); }
.mt-6 { margin-top: var(--sp-6); }
.mt-8 { margin-top: var(--sp-8); }
.mt-12 { margin-top: var(--sp-12); }
.mb-4 { margin-bottom: var(--sp-4); }
.mb-6 { margin-bottom: var(--sp-6); }
.mb-8 { margin-bottom: var(--sp-8); }
.mb-12 { margin-bottom: var(--sp-12); }

/* ==========================================================================
   响应式
   ========================================================================== */

@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .section { padding-block: var(--sp-16); }
}

@media (max-width: 720px) {
  body { font-size: var(--fs-15); }
  .wrap { padding-inline: var(--sp-5); }
  .grid-2, .grid-3, .grid-4 { grid-template-columns: minmax(0, 1fr); }
  .section { padding-block: var(--sp-12); }
  .t-lead { font-size: var(--fs-16); }
}