/* base.css — 变量 / 重置 / 排版 / 基础背景 */
:root {
  --bg: #07070c;
  --bg-2: #0b0b16;
  --surface: rgba(255, 255, 255, 0.04);
  --surface-2: rgba(255, 255, 255, 0.07);
  --border: rgba(255, 255, 255, 0.09);
  --border-strong: rgba(255, 255, 255, 0.16);
  --text: #ecebf5;
  --muted: #9a9ab5;
  --grad: linear-gradient(135deg, #a78bfa, #22d3ee 52%, #f472b6);
  --radius: 18px;
  --maxw: 1140px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

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

html { scroll-behavior: smooth; }

body {
  min-height: 100vh;
  background: var(--bg);
  color: var(--text);
  font-family: "Inter", system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  overflow-x: hidden;
  position: relative;
  -webkit-font-smoothing: antialiased;
}

/* 叠在纯黑之上的基础径向底色 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -3;
  background:
    radial-gradient(1200px 600px at 15% -10%, rgba(139, 92, 246, 0.18), transparent 60%),
    radial-gradient(1000px 700px at 100% 0%, rgba(34, 211, 238, 0.12), transparent 55%),
    linear-gradient(180deg, var(--bg), var(--bg-2));
}

h1, h2, h3,
.nav__logo,
.btn {
  font-family: "Space Grotesk", "Inter", sans-serif;
  letter-spacing: -0.02em;
}

a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
::selection { background: rgba(139, 92, 246, 0.4); color: #fff; }

/* 渐变文字工具类 */
.grad {
  background: var(--grad);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  background-size: 200% auto;
}

/* 键盘可达性:清晰的焦点环 */
:focus-visible {
  outline: 2px solid #22d3ee;
  outline-offset: 3px;
  border-radius: 6px;
}

::-webkit-scrollbar { width: 10px; }
::-webkit-scrollbar-thumb {
  background: rgba(139, 92, 246, 0.35);
  border-radius: 10px;
}