/* ==========================================================================
   base.css — 重置、排版基元、焦点与降级（三套界面共用）
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  /* 横向裁切放在 html：避免 body 因 overflow 计算规则变成滚动容器而破坏 sticky */
  overflow-x: hidden;
}

body {
  margin: 0;
  min-height: 100dvh;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--ff-sans);
  font-size: var(--fs-md);
  line-height: var(--lh-body);
  letter-spacing: var(--tr-cn);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* hidden 必须压过组件的 display 声明（.btn / .empty / .field 等都设了 display） */
[hidden] { display: none !important; }

h1, h2, h3, h4, p, figure, blockquote, dl, dd { margin: 0; }
ul, ol { margin: 0; padding: 0; list-style: none; }
a { color: inherit; text-decoration: none; }
button, input, select, textarea { font: inherit; color: inherit; letter-spacing: inherit; }
button { background: none; border: 0; padding: 0; cursor: pointer; }
img, svg, video { display: block; max-width: 100%; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: var(--r-xs); }
:focus:not(:focus-visible) { outline: none; }
::selection { background: var(--accent-soft); color: var(--ink); }

* { scrollbar-width: thin; scrollbar-color: var(--line-strong) transparent; }
*::-webkit-scrollbar { width: 10px; height: 10px; }
*::-webkit-scrollbar-track { background: transparent; }
*::-webkit-scrollbar-thumb {
  background: var(--line-strong);
  border: 3px solid transparent;
  background-clip: content-box;
  border-radius: var(--r-full);
}
*::-webkit-scrollbar-thumb:hover { background: var(--ink-3); background-clip: content-box; }

/* ==========================================================================
   排版基元
   ========================================================================== */
.u-display {
  font-family: var(--ff-display);
  font-weight: 400;
  letter-spacing: var(--tr-tight);
  line-height: var(--lh-tight);
  text-transform: uppercase;
}
.u-mono { font-family: var(--ff-mono); font-variant-numeric: tabular-nums; }
.u-label {
  font-family: var(--ff-mono);
  font-size: var(--fs-2xs);
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-3);
}
.u-num {
  font-family: var(--ff-mono);
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum" 1;
}
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip-path: inset(50%); white-space: nowrap;
}
.skip-link {
  position: fixed; top: var(--sp-2); left: var(--sp-2); z-index: 999;
  padding: 10px 16px;
  background: var(--accent); color: var(--accent-ink);
  font-size: var(--fs-sm); border-radius: var(--r-sm);
  transform: translateY(-200%);
  transition: transform var(--dur-fast) var(--ease-out);
}
.skip-link:focus-visible { transform: none; }

/* ==========================================================================
   降级：系统开启"减少动态效果"时，位移与缩放一律归零
   ========================================================================== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
  :root { --lift: 0px; --enter-y: 0px; --stagger: 0ms; }
}