/* ============================================================
   base.css — 重置、排版、布局原语、背景层
   ============================================================ */
*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-h) + 16px);
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg-base);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: var(--fs-15);
  line-height: 1.75;
  font-weight: 350;
  letter-spacing: 0.01em;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

body.is-locked { overflow: hidden; }

h1, h2, h3, h4 {
  margin: 0;
  color: var(--text-hi);
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.22;
  letter-spacing: -0.015em;
}

p { margin: 0; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; cursor: pointer; }
input { font: inherit; }
img, svg { display: block; max-width: 100%; }
ul { margin: 0; padding: 0; list-style: none; }

::selection { background: rgba(56, 225, 255, 0.28); color: #fff; }

:focus-visible {
  outline: 2px solid var(--brand-blue);
  outline-offset: 3px;
  border-radius: 4px;
}

/* 滚动条 */
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg-deep); }
::-webkit-scrollbar-thumb {
  background: linear-gradient(180deg, #1d2b45, #16223a);
  border-radius: 99px;
  border: 2px solid var(--bg-deep);
}
::-webkit-scrollbar-thumb:hover { background: linear-gradient(180deg, #2b405f, #1e2d4a); }

/* ---------- 布局原语 ---------- */
.container {
  width: min(100% - 40px, var(--container));
  margin-inline: auto;
}
.container--narrow { width: min(100% - 40px, var(--container-narrow)); }

.section { position: relative; padding-block: var(--section-gap); }

/* ---------- 通用排版件 ---------- */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
  font-family: var(--font-mono);
  font-size: var(--fs-12);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--brand-blue);
  padding: 5px 12px 5px 10px;
  border: 1px solid var(--line);
  border-radius: var(--r-pill);
  background: rgba(56, 225, 255, 0.06);
}
.eyebrow::before {
  content: "";
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--brand-blue);
  box-shadow: 0 0 10px var(--brand-blue);
  animation: pulse 2.4s var(--ease) infinite;
}

.section__head { max-width: 760px; margin-bottom: var(--sp-7); }
.section__head--center { margin-inline: auto; text-align: center; }

.section__title {
  font-size: var(--fs-40);
  margin-block: var(--sp-4) var(--sp-3);
  background: var(--grad-text);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.section__sub { color: var(--text-dim); font-size: var(--fs-16); }

.mono { font-family: var(--font-mono); }
.grad-text {
  background: var(--grad-brand);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.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;
}

/* ---------- 背景层 ---------- */
.bg-layer {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background:
    radial-gradient(120% 80% at 50% -10%, #0a1224 0%, transparent 60%),
    linear-gradient(180deg, #04060c 0%, #05070f 40%, #04060c 100%);
}
.bg-grid {
  position: absolute; inset: 0;
  background-image:
    linear-gradient(rgba(110, 160, 220, 0.055) 1px, transparent 1px),
    linear-gradient(90deg, rgba(110, 160, 220, 0.055) 1px, transparent 1px);
  background-size: 56px 56px;
  mask-image: radial-gradient(110% 75% at 50% 20%, #000 0%, transparent 78%);
  -webkit-mask-image: radial-gradient(110% 75% at 50% 20%, #000 0%, transparent 78%);
}
.bg-glow { position: absolute; border-radius: 50%; filter: blur(90px); opacity: 0.5; }
.bg-glow--a {
  width: 46vw; height: 46vw; top: -12vw; left: -8vw;
  background: radial-gradient(circle, rgba(56, 225, 255, 0.32), transparent 65%);
  animation: drift 24s ease-in-out infinite alternate;
}
.bg-glow--b {
  width: 40vw; height: 40vw; top: 42vh; right: -12vw;
  background: radial-gradient(circle, rgba(139, 107, 255, 0.3), transparent 65%);
  animation: drift 30s ease-in-out infinite alternate-reverse;
}
.bg-noise {
  position: absolute; inset: 0; opacity: 0.16; mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)' opacity='0.5'/%3E%3C/svg%3E");
}
.bg-scan {
  position: absolute; inset: 0; opacity: 0.35;
  background: repeating-linear-gradient(180deg, rgba(255,255,255,0.018) 0 1px, transparent 1px 3px);
}

/* ---------- 动效 ---------- */
@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.4; transform: scale(0.7); }
}
@keyframes drift {
  0% { transform: translate3d(0, 0, 0) scale(1); }
  100% { transform: translate3d(6vw, 5vh, 0) scale(1.12); }
}
@keyframes riseIn {
  from { opacity: 0; transform: translateY(26px); }
  to { opacity: 1; transform: none; }
}
@keyframes spin { to { transform: rotate(360deg); } }
@keyframes marquee {
  from { transform: translateX(0); }
  to { transform: translateX(-50%); }
}

/* 入场动画：由 JS 给元素加 .is-in */
.reveal {
  opacity: 0;
  transform: translateY(26px);
  transition: opacity 0.7s var(--ease-out), transform 0.7s var(--ease-out);
}
.reveal.is-in { opacity: 1; transform: none; }
.reveal[data-delay="1"] { transition-delay: 0.08s; }
.reveal[data-delay="2"] { transition-delay: 0.16s; }
.reveal[data-delay="3"] { transition-delay: 0.24s; }
.reveal[data-delay="4"] { transition-delay: 0.32s; }
.reveal[data-delay="5"] { transition-delay: 0.4s; }

/* ---------- noscript / fab ---------- */
.noscript {
  max-width: 640px;
  margin: 18vh auto;
  padding: var(--sp-6);
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--panel);
  text-align: center;
}
.noscript h1 { font-size: var(--fs-32); margin-bottom: var(--sp-3); }

.kb-fab {
  position: fixed;
  right: clamp(16px, 3vw, 28px);
  bottom: clamp(16px, 3vw, 28px);
  z-index: var(--z-fab);
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 16px;
  border: 1px solid var(--line-hi);
  border-radius: var(--r-pill);
  background: rgba(10, 16, 30, 0.82);
  backdrop-filter: blur(14px);
  color: var(--text-hi);
  font-size: var(--fs-13);
  font-weight: 500;
  box-shadow: var(--glow-blue);
  transition: transform 0.3s var(--ease-out), box-shadow 0.3s var(--ease-out), border-color 0.3s;
}
.kb-fab:hover { transform: translateY(-3px); border-color: var(--brand-blue); }
.kb-fab__icon { font-size: 17px; line-height: 1; color: var(--brand-blue); }
.kb-fab kbd {
  font-family: var(--font-mono);
  font-size: 11px;
  padding: 2px 6px;
  border: 1px solid var(--line);
  border-radius: 5px;
  color: var(--text-dim);
  background: rgba(255, 255, 255, 0.04);
}

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