/* ============================================================
   base.css — 基础重置与通用工具
   ============================================================ */

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

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

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--fs-body);
  line-height: var(--lh-body);
  color: var(--text-primary);
  background: var(--bg-page);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  transition: background-color var(--dur-base) var(--ease-out), color var(--dur-base) var(--ease-out);
}

h1, h2, h3, h4, p { margin: 0; }
h1 { font-size: var(--fs-h1); line-height: var(--lh-h1); font-weight: 700; }
h2 { font-size: var(--fs-h2); line-height: var(--lh-h2); font-weight: 650; }
h3 { font-size: var(--fs-h3); line-height: var(--lh-h3); font-weight: 600; }

a { color: inherit; text-decoration: none; }
button { font-family: inherit; }
img, video, svg { display: block; max-width: 100%; }
ul, ol { margin: 0; padding: 0; list-style: none; }

::selection { background: var(--brand-500); color: #fff; }

/* 滚动条 */
* { scrollbar-width: thin; scrollbar-color: var(--border-strong) transparent; }
*::-webkit-scrollbar { width: 8px; height: 8px; }
*::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 4px; }
*::-webkit-scrollbar-track { background: transparent; }

/* 数字等宽 */
.num { font-variant-numeric: tabular-nums; }

/* 文本截断 */
.ellipsis { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.clamp-2 { display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }

/* ---------- 布局工具 ---------- */
.container { max-width: var(--w-container); margin: 0 auto; padding: 0 var(--sp-5); }
.container-wide { max-width: var(--w-container-wide); margin: 0 auto; padding: 0 var(--sp-5); }

/* 渐变文字 */
.grad-text {
  background: var(--brand-grad);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
}

/* ---------- 滚动进入动画（IntersectionObserver 触发） ---------- */
.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity var(--dur-slow) var(--ease-out), transform var(--dur-slow) var(--ease-out);
  transition-delay: var(--reveal-delay, 0s);
  will-change: opacity, transform;
}
.reveal.is-in { opacity: 1; transform: none; }

/* 减少动态偏好 */
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; }
}

/* ---------- 通用表单基础 ---------- */
input, textarea, select {
  font-family: inherit;
  font-size: var(--fs-body);
  color: var(--text-primary);
  background: var(--bg-inset);
  border: 1px solid var(--border);
  border-radius: var(--r-sm);
  outline: none;
  transition: border-color var(--dur-fast) ease, box-shadow var(--dur-fast) ease, background var(--dur-fast) ease;
}
input:focus, textarea:focus, select:focus {
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--brand-soft);
}
input::placeholder, textarea::placeholder { color: var(--text-tertiary); }

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