/* ==========================================================================
   基础层 —— 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;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  margin: 0;
  font-weight: 400;
  line-height: 0.98;
  letter-spacing: -0.03em;
}

p { margin: 0; }

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

a {
  color: inherit;
  text-decoration: none;
}

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

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

ul, ol {
  margin: 0;
  padding: 0;
  list-style: none;
}

/* --- 焦点：必须可见，键盘用户优先 ------------------------------------- */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

::selection {
  background: var(--color-accent);
  color: var(--color-accent-ink);
}

/* --- 氛围层：极细网格 + 颗粒，营造技术图纸感 --------------------------- */
.atmosphere::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, var(--color-line) 1px, transparent 1px),
    linear-gradient(to bottom, var(--color-line) 1px, transparent 1px);
  background-size: 120px 120px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, #000 20%, transparent 75%);
  opacity: 0.55;
}

.atmosphere::after {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  opacity: 0.035;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='140' height='140' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* --- 工具类 ----------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: var(--gutter);
  position: relative;
  z-index: 2;
}

.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.02em;
}

.label {
  font-family: var(--font-mono);
  font-size: var(--text-2xs);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-muted);
}

.display {
  font-family: var(--font-display);
  text-transform: uppercase;
  letter-spacing: -0.03em;
}

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

.skip-link {
  position: absolute;
  top: -100px;
  left: var(--space-3);
  z-index: 999;
  padding: var(--space-2) var(--space-3);
  background: var(--color-accent);
  color: var(--color-accent-ink);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
}

.skip-link:focus {
  top: var(--space-3);
}

/* --- 入场：一次编排好的错峰序列 --------------------------------------- */
/* 只有 JS 可用时才隐藏，避免脚本失败导致整页空白 / 打印时内容丢失 */
.js .reveal {
  opacity: 0;
  transform: translateY(22px);
}

.js .reveal.in {
  opacity: 1;
  transform: none;
  transition:
    opacity var(--dur-slow) var(--ease-out),
    transform var(--dur-slow) var(--ease-out);
}

.reveal[data-delay="1"] { transition-delay: 80ms; }
.reveal[data-delay="2"] { transition-delay: 160ms; }
.reveal[data-delay="3"] { transition-delay: 240ms; }
.reveal[data-delay="4"] { transition-delay: 320ms; }

/* --- 动效降级：系统层面关掉 ------------------------------------------------- */
@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;
    scroll-behavior: auto !important;
  }

  .reveal {
    opacity: 1;
    transform: none;
  }
}