:root {
  --bg: #f7f8fa;
  --surface: #ffffff;
  --text: #1a1f27;
  --muted: #5c6570;
  --accent: #2563eb;
  --accent-2: #7c3aed;
  --border: #e6e9ee;
  --radius: 14px;
  --shadow: 0 10px 30px rgba(20, 30, 50, 0.08);
  --maxw: 1080px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Nav */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  display: flex; align-items: center; justify-content: space-between;
  height: 64px;
}
.brand { font-weight: 700; font-size: 1.15rem; color: var(--text); }
.nav-links { display: flex; gap: 28px; }
.nav-links a { color: var(--muted); font-weight: 500; }
.nav-links a:hover { color: var(--text); }
.nav-toggle {
  display: none; background: none; border: none;
  font-size: 1.4rem; cursor: pointer; color: var(--text);
}

/* Hero */
.hero {
  padding: 120px 24px 90px;
  background:
    radial-gradient(60% 120% at 15% 0%, rgba(37, 99, 235, 0.12), transparent 60%),
    radial-gradient(50% 100% at 85% 20%, rgba(124, 58, 237, 0.12), transparent 60%);
}
.hero-inner { max-width: var(--maxw); margin: 0 auto; }
.hero-hello { color: var(--muted); font-size: 1.1rem; margin-bottom: 8px; }
.hero h1 {
  font-size: clamp(2.6rem, 6vw, 4.2rem);
  letter-spacing: -0.02em; line-height: 1.1; margin-bottom: 18px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero-tagline { color: var(--muted); font-size: 1.25rem; max-width: 560px; margin-bottom: 32px; }
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; }
.btn {
  display: inline-block; padding: 12px 26px; border-radius: 999px;
  font-weight: 600; font-size: 1rem; transition: transform .15s ease, box-shadow .15s ease;
}
.btn:hover { text-decoration: none; transform: translateY(-2px); }
.btn-primary { background: linear-gradient(90deg, var(--accent), var(--accent-2)); color: #fff; box-shadow: 0 8px 20px rgba(37, 99, 235, 0.3); }
.btn-ghost { border: 1px solid var(--border); color: var(--text); background: var(--surface); }

/* Sections */
.section { padding: 80px 24px; }
.section-alt { background: var(--surface); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.section-inner { max-width: var(--maxw); margin: 0 auto; }
.section h2 { font-size: 2rem; margin-bottom: 20px; letter-spacing: -0.01em; }
.lead { color: var(--muted); font-size: 1.1rem; max-width: 640px; margin-bottom: 40px; }

.about-grid, .projects-grid {
  display: grid; gap: 20px; grid-template-columns: repeat(3, 1fr);
}
.about-card, .project-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 26px; box-shadow: var(--shadow);
}
.section-alt .about-card { background: var(--bg); }
.about-card h3, .project-card h3 { font-size: 1.15rem; margin-bottom: 10px; }
.about-card p, .project-card p { color: var(--muted); }
.project-link { display: inline-block; margin-top: 14px; font-weight: 600; }

.contact-list { list-style: none; display: grid; gap: 14px; max-width: 460px; }
.contact-list li { display: flex; gap: 12px; align-items: baseline; padding: 14px 18px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); }
.contact-list span { color: var(--muted); min-width: 84px; }

.footer { text-align: center; padding: 36px 24px; color: var(--muted); font-size: .92rem; border-top: 1px solid var(--border); }

/* Responsive */
@media (max-width: 820px) {
  .about-grid, .projects-grid { grid-template-columns: 1fr; }
  .nav-toggle { display: block; }
  .nav-links {
    display: none; position: absolute; top: 64px; left: 0; right: 0;
    flex-direction: column; gap: 0; background: var(--surface);
    border-bottom: 1px solid var(--border); padding: 8px 24px;
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 14px 0; }
}