/* ============================================================================
   base.css · 重置 / 排版 / 焦点 / 氛围 / 动效降级
   ========================================================================== */

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

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

body {
  margin: 0;
  min-height: 100vh;
  background: var(--c-bg);
  color: var(--c-text);
  font-family: var(--f-body);
  font-size: var(--fs-md);
  font-weight: 400;
  line-height: 1.7;
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  margin: 0;
  font-family: var(--f-display);
  font-weight: 700;
  line-height: 1.15;
  letter-spacing: -0.01em;
}
/* 字号不做负字距：中文在小字号下收紧会糊，孩子阅读优先 */
h1 { font-size: var(--fs-3xl); }
h2 { font-size: var(--fs-2xl); }
h3 { font-size: var(--fs-xl); }
h4 { font-size: var(--fs-lg); }

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

button, input, select, textarea {
  font: inherit; color: inherit; background: none; border: none;
}
button { cursor: pointer; }

.mono, .num, output, time, data {
  font-family: var(--f-mono);
  font-variant-numeric: tabular-nums;
  font-feature-settings: 'tnum' 1;
}

/* --- 焦点可见：孩子用键盘的场景少，但这是可访问性底线 --------------------- */
:focus-visible {
  outline: 3px solid var(--c-accent);
  outline-offset: 3px;
  border-radius: var(--r-xs);
}
:focus:not(:focus-visible) { outline: none; }

/* --- 工具类 ------------------------------------------------------------- */
.wrap { width: min(100% - var(--s-4) * 2, 1180px); margin-inline: auto; }
.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;
}
.stack   { display: grid; gap: var(--s-3); }
.stack-4 { display: grid; gap: var(--s-4); }
.row     { display: flex; align-items: center; gap: var(--s-3); flex-wrap: wrap; }
.grow    { flex: 1 1 auto; min-width: 0; }

.eyebrow {
  display: inline-flex; align-items: center; gap: var(--s-2);
  font-family: var(--f-mono); font-size: var(--fs-xs); font-weight: 500;
  letter-spacing: 0.2em; text-transform: uppercase; color: var(--c-accent);
}
.eyebrow::before {
  content: ''; width: 7px; height: 7px; flex: none; border-radius: 50%;
  background: var(--c-accent); box-shadow: 0 0 12px var(--c-accent);
}
.lede { color: var(--c-text-dim); max-width: 60ch; }

/* --- 氛围：暗底上的两团柔光（品牌蓝为主，一点金呼应金币插画），避免大面积死平 */
body::before {
  content: ''; position: fixed; inset: 0; pointer-events: none; z-index: 0;
  background:
    radial-gradient(46rem 34rem at 10% -10%, rgba(77, 125, 255, 0.13), transparent 62%),
    radial-gradient(40rem 30rem at 100% 8%, rgba(255, 194, 51, 0.06), transparent 58%);
}

/* --- 入场：一次编排好的序列，按 70ms 错峰 -------------------------------- */
.reveal { opacity: 0; transform: translateY(18px); }
.reveal.is-in {
  opacity: 1; transform: none;
  transition: opacity var(--dur-slow) var(--ease-out),
              transform var(--dur-slow) var(--ease-bounce);
  transition-delay: var(--reveal-delay, 0ms);
}
.reveal[data-i='1'] { --reveal-delay: 70ms; }
.reveal[data-i='2'] { --reveal-delay: 140ms; }
.reveal[data-i='3'] { --reveal-delay: 210ms; }
.reveal[data-i='4'] { --reveal-delay: 280ms; }
.reveal[data-i='5'] { --reveal-delay: 350ms; }

/* --- 动效降级 ----------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
  .reveal { opacity: 1 !important; transform: none !important; }
}