/* ==========================================================================
   玥耀 FPGA — Base Layer
   重置 / 排版 / 栅格 / 通用工具 / 动效与可访问性
   ========================================================================== */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 24px);
}

body {
  margin: 0;
  min-width: 320px;
  overflow-x: hidden;               /* 禁止横向滚动 */
  background-color: var(--c-bg-900);
  background-image:
    radial-gradient(1100px 560px at 78% -8%, rgba(59, 130, 246, 0.16), transparent 62%),
    radial-gradient(880px 480px at 4% 4%, rgba(124, 58, 237, 0.10), transparent 64%),
    linear-gradient(180deg, #080B12 0%, #0B0F18 42%, #080B12 100%);
  background-attachment: fixed;
  color: var(--c-text-200);
  font-family: var(--font-sans);
  font-size: var(--fs-body);
  line-height: var(--lh-normal);
  font-weight: var(--fw-regular);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* 全局电路网格底纹（固定，低对比，不参与交互） */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  background-image:
    linear-gradient(to right, rgba(148, 163, 184, 0.055) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(148, 163, 184, 0.055) 1px, transparent 1px);
  background-size: 72px 72px;
  -webkit-mask-image: radial-gradient(1200px 700px at 50% 0%, #000 0%, transparent 78%);
          mask-image: radial-gradient(1200px 700px at 50% 0%, #000 0%, transparent 78%);
}

h1, h2, h3, h4, h5, h6 {
  margin: 0;
  color: var(--c-text-100);
  font-weight: var(--fw-semibold);
  line-height: var(--lh-snug);
  letter-spacing: var(--ls-tight);
}

p { margin: 0; }

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--t-fast);
}

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

/* 作者样式中的 display 声明会覆盖 UA 对 [hidden] 的默认处理，
   这里显式兜底，确保 hidden 属性在任何组件上都生效 */
[hidden] { display: none !important; }

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

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

hr {
  border: 0;
  border-top: 1px solid var(--c-border-soft);
  margin: 0;
}

::selection { background: rgba(59, 130, 246, 0.35); color: #fff; }

/* 滚动条（桌面端） */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--c-bg-900); }
::-webkit-scrollbar-thumb {
  background: rgba(148, 163, 184, 0.22);
  border-radius: var(--r-pill);
  border: 2px solid var(--c-bg-900);
}
::-webkit-scrollbar-thumb:hover { background: rgba(148, 163, 184, 0.38); }

/* ==========================================================================
   布局容器 / 12 栏栅格
   ========================================================================== */

.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--sp-10);
  position: relative;
  z-index: 1;
}

.container--wide { max-width: 1440px; }
.container--narrow { max-width: 920px; }

.grid-12 {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: var(--gutter);
  align-items: start;
}

.col-3  { grid-column: span 3; }
.col-4  { grid-column: span 4; }
.col-5  { grid-column: span 5; }
.col-6  { grid-column: span 6; }
.col-7  { grid-column: span 7; }
.col-8  { grid-column: span 8; }
.col-9  { grid-column: span 9; }
.col-12 { grid-column: span 12; }

.section { padding-block: var(--section-y); position: relative; }
.section--tight { padding-block: var(--section-y-sm); }
.section--line { border-top: 1px solid var(--c-border-soft); }

.stack-4 > * + * { margin-top: var(--sp-4); }
.stack-6 > * + * { margin-top: var(--sp-6); }
.stack-8 > * + * { margin-top: var(--sp-8); }

@media (max-width: 1023px) {
  .container { padding-inline: var(--sp-6); }
  .md-col-6  { grid-column: span 6; }
  .md-col-12 { grid-column: span 12; }
}

@media (max-width: 767px) {
  .container { padding-inline: var(--sp-4); }
  .grid-12 { gap: var(--sp-4); }
  .col-3, .col-4, .col-5, .col-6, .col-7, .col-8, .col-9 { grid-column: span 12; }
  .sm-col-6 { grid-column: span 6; }
}

/* ==========================================================================
   排版工具
   ========================================================================== */

.t-display { font-size: var(--fs-display); line-height: var(--lh-tight); letter-spacing: var(--ls-tight); }
.t-h1 { font-size: var(--fs-h1); }
.t-h2 { font-size: var(--fs-h2); }
.t-h3 { font-size: var(--fs-h3); }
.t-h4 { font-size: var(--fs-h4); }
.t-lead { font-size: var(--fs-lead); line-height: var(--lh-loose); color: var(--c-text-300); font-weight: var(--fw-regular); }
.t-body { font-size: var(--fs-body); line-height: var(--lh-loose); color: var(--c-text-300); }
.t-sm   { font-size: var(--fs-sm); color: var(--c-text-300); line-height: var(--lh-normal); }
.t-caption { font-size: var(--fs-caption); color: var(--c-text-300); }

.t-mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.t-en { font-family: var(--font-display); }

.t-strong { color: var(--c-text-100); font-weight: var(--fw-medium); }
.t-accent { color: var(--c-accent-400); }
.t-brand  { color: var(--c-brand-400); }

.eyebrow {
  font-family: var(--font-mono);
  font-size: var(--fs-caption);
  letter-spacing: var(--ls-wider);
  text-transform: uppercase;
  color: var(--c-brand-400);
}

.section-head { max-width: 760px; }
.section-head .t-h2 { margin-top: var(--sp-4); }
.section-head .t-body { margin-top: var(--sp-4); }

.measure { max-width: 62ch; }
.hairline { height: 1px; background: var(--c-border-soft); }
.mt-2 { margin-top: var(--sp-2); } .mt-4 { margin-top: var(--sp-4); }
.mt-6 { margin-top: var(--sp-6); } .mt-8 { margin-top: var(--sp-8); }
.mt-10 { margin-top: var(--sp-10); } .mt-12 { margin-top: var(--sp-12); }

/* 装饰性斜切角（工程感切角） */
.corner-cut {
  clip-path: polygon(0 0, calc(100% - 12px) 0, 100% 12px, 100% 100%, 12px 100%, 0 calc(100% - 12px));
}

/* ==========================================================================
   动效
   ========================================================================== */

.reveal {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity var(--t-slow), transform var(--t-slow);
  will-change: opacity, transform;
}
.reveal.is-in { opacity: 1; transform: none; }

@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; }
}

/* ==========================================================================
   可访问性
   ========================================================================== */

:focus-visible {
  outline: 2px solid var(--c-accent-400);
  outline-offset: 2px;
  border-radius: var(--r-xs);
}

.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;
}

.skip-link {
  position: absolute;
  top: -60px; left: var(--sp-4);
  z-index: 999;
  padding: var(--sp-3) var(--sp-5);
  background: var(--c-brand-600);   /* 白字 5.17:1；用 brand-500 仅 3.68:1 */
  color: #fff;
  border-radius: var(--r-sm);
  font-size: var(--fs-sm);
  transition: top var(--t-fast);
}
.skip-link:focus { top: var(--sp-3); }

/* 图标统一规格 */
.icon { width: 22px; height: 22px; flex: none; stroke: currentColor; fill: none; stroke-width: 1.5; stroke-linecap: round; stroke-linejoin: round; }
.icon--lg { width: 28px; height: 28px; }
.icon--sm { width: 16px; height: 16px; }