/* ============================================================
   base.css — Reset、排版、工具类、无障碍
   ============================================================ */

/* ---- Reset ---- */
*,*::before,*::after { box-sizing:border-box; margin:0; padding:0; }

html {
  scroll-behavior:smooth;
  font-size:var(--fs-base);
  -webkit-text-size-adjust:100%;
}

body {
  font-family:var(--font-body);
  line-height:var(--lh);
  color:var(--c-text);
  background:var(--c-bg);
  min-height:100vh;
  -webkit-font-smoothing:antialiased;
  -moz-osx-font-smoothing:grayscale;
}

img, picture, video, canvas, svg { display:block; max-width:100%; }
img { height:auto; }
input, button, textarea, select { font:inherit; color:inherit; }
a { color:inherit; text-decoration:none; }
ul, ol { list-style:none; }
h1,h2,h3,h4,h5,h6 { line-height:var(--lh-heading); color:var(--c-heading); font-weight:700; }
h1 { font-size:var(--fs-h1); }
h2 { font-size:var(--fs-h2); }
h3 { font-size:var(--fs-h3); }
h4 { font-size:var(--fs-h4); }
p { margin-bottom:1em; }
p:last-child { margin-bottom:0; }
strong { font-weight:700; }

/* ---- Focus ---- */
:focus-visible {
  outline:2px solid var(--c-primary);
  outline-offset:2px;
  border-radius:2px;
}

/* ---- Skip link ---- */
.skip-link {
  position:absolute;
  top:-100%;
  left:var(--space-md);
  background:var(--c-primary);
  color:#fff;
  padding:.5em 1em;
  z-index:10000;
  border-radius:var(--radius);
  font-weight:700;
  font-size:var(--fs-sm);
}
.skip-link:focus { top:var(--space-sm); }

/* ---- Selection ---- */
::selection {
  background:var(--c-primary);
  color:#fff;
}

/* ---- Scrollbar (pixel-modern) ---- */
html {
  scrollbar-width: thin;
  scrollbar-color: var(--c-border) var(--c-bg);
}
::-webkit-scrollbar { width:10px; height:10px; }
::-webkit-scrollbar-track {
  background:var(--c-bg);
  border-left:1px solid var(--c-border);
}
::-webkit-scrollbar-thumb {
  background:var(--c-border);
  border-radius:var(--radius);
  border:2px solid var(--c-bg);
  transition:background var(--duration);
}
::-webkit-scrollbar-thumb:hover { background:var(--c-primary); }
::-webkit-scrollbar-thumb:active { background:var(--c-primary-dark); }

[data-theme="dark"] ::-webkit-scrollbar-track { border-color:var(--c-border); }
[data-theme="dark"] ::-webkit-scrollbar-thumb { background:var(--c-border); }
[data-theme="dark"] ::-webkit-scrollbar-thumb:hover { background:var(--c-primary); }

/* ---- Typography helpers ---- */
.text-mono  { font-family:var(--font-mono); letter-spacing:0; }
.text-muted { color:var(--c-text-muted); }
.text-sm    { font-size:var(--fs-sm); }
.text-xs    { font-size:var(--fs-xs); }
.text-lg    { font-size:var(--fs-lg); }
.text-center { text-align:center; }

/* ---- Links inside prose ---- */
.prose a {
  color:var(--c-primary);
  text-decoration:underline;
  text-underline-offset:2px;
}
.prose a:hover { color:var(--c-primary-hi); }

/* ---- Utility: container ---- */
.container {
  width:100%;
  max-width:var(--max-width);
  margin-inline:auto;
  padding-inline:var(--space-lg);
}

/* ---- Utility: visually hidden ---- */
.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;
}

/* ---- Utility: section spacing ---- */
.section {
  padding-block:var(--space-3xl);
}
.section-sm {
  padding-block:var(--space-2xl);
}
.section-alt {
  background:var(--c-bg-section-alt);
}

/* ---- Reduced motion ---- */
@media (prefers-reduced-motion:reduce) {
  html { scroll-behavior:auto; }
  *,*::before,*::after { animation-duration:.01ms !important; animation-iteration-count:1 !important; transition-duration:.01ms !important; }
}

/* ---- Print ---- */
@media print {
  .site-header, .site-footer, .back-to-top, .no-print { display:none !important; }
  body { background:#fff; color:#000; }
}