:root {
  --color-bg: #ffffff;
  --color-text: #1a1a1a;
  --color-text-muted: #666666;
  --color-border: #e6e6e6;
  --color-border-strong: #1a1a1a;
  --color-accent: #000000;

  --font-sans: -apple-system, BlinkMacSystemFont, "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;

  --space-1: 0.5rem;
  --space-2: 1rem;
  --space-3: 1.5rem;
  --space-4: 2rem;
  --space-6: 3rem;
  --space-8: 5rem;
  --space-12: 8rem;

  --max-width: 880px;
  --radius: 4px;
}

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

html {
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  * {
    animation: none !important;
    transition: none !important;
  }
}

body {
  margin: 0;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-sans);
  font-size: clamp(15px, 1vw + 0.6rem, 18px);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

a {
  color: var(--color-text);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s ease;
}

a:hover,
a:focus-visible {
  border-bottom-color: var(--color-text);
}

a:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-3);
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(8px);
  -webkit-backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--color-border);
  z-index: 10;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: var(--space-2);
  padding-bottom: var(--space-2);
}

.logo {
  font-weight: 600;
  font-size: 1rem;
  letter-spacing: -0.01em;
}

.nav {
  display: flex;
  gap: var(--space-3);
  font-size: 0.95rem;
}

/* Hero */
.hero {
  padding-top: var(--space-12);
  padding-bottom: var(--space-12);
}

.hero-title {
  font-size: clamp(2.25rem, 5vw + 1rem, 4rem);
  line-height: 1.1;
  letter-spacing: -0.02em;
  font-weight: 700;
  margin: 0 0 var(--space-3);
}

.hero-subtitle {
  font-size: clamp(1rem, 0.6vw + 0.9rem, 1.25rem);
  color: var(--color-text-muted);
  margin: 0 0 var(--space-6);
  max-width: 36rem;
}

.cta {
  display: inline-block;
  font-weight: 500;
  padding: 0.65rem 1.25rem;
  border: 1px solid var(--color-border-strong);
  border-radius: var(--radius);
  border-bottom: 1px solid var(--color-border-strong);
}

.cta:hover,
.cta:focus-visible {
  background: var(--color-text);
  color: var(--color-bg);
  border-bottom-color: var(--color-text);
}

/* Sections */
section + section {
  margin-top: var(--space-8);
}

.about,
.projects {
  padding-top: var(--space-8);
  padding-bottom: var(--space-8);
  border-top: 1px solid var(--color-border);
}

.section-title {
  font-size: clamp(1.5rem, 1.5vw + 1rem, 2rem);
  letter-spacing: -0.01em;
  margin: 0 0 var(--space-4);
  font-weight: 600;
}

.lede {
  font-size: 1.05rem;
  max-width: 42rem;
  margin: 0 0 var(--space-4);
}

.skills {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-1);
}

.skills li {
  font-size: 0.85rem;
  color: var(--color-text-muted);
  padding: 0.25rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: 999px;
}

/* Projects grid */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: var(--space-3);
}

.card {
  padding: var(--space-3);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  transition: border-color 0.2s ease;
  display: flex;
  flex-direction: column;
}

.card:hover {
  border-color: var(--color-border-strong);
}

.card-title {
  margin: 0 0 var(--space-1);
  font-size: 1.15rem;
  font-weight: 600;
}

.card-desc {
  margin: 0 0 var(--space-2);
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.card-tags {
  margin: 0 0 var(--space-3);
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.card-tags span {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  padding: 0.15rem 0.55rem;
  background: #f5f5f5;
  border-radius: 3px;
}

.card-link {
  margin-top: auto;
  font-size: 0.9rem;
  font-weight: 500;
}

/* Footer */
.site-footer {
  margin-top: var(--space-8);
  border-top: 1px solid var(--color-border);
  padding-top: var(--space-4);
  padding-bottom: var(--space-4);
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-2);
}

.footer-inner p {
  margin: 0;
}

.beian a {
  color: var(--color-text-muted);
}

.beian a:hover,
.beian a:focus-visible {
  color: var(--color-text);
  border-bottom-color: var(--color-text);
}

.contact a {
  color: var(--color-text-muted);
}

.contact a:hover,
.contact a:focus-visible {
  color: var(--color-text);
  border-bottom-color: var(--color-text);
}

.contact span {
  margin: 0 0.4em;
  color: var(--color-border);
}

/* 404 specific */
.notfound {
  min-height: 60vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--space-8) var(--space-3);
}

.notfound h1 {
  font-size: clamp(3rem, 6vw + 1rem, 5rem);
  margin: 0 0 var(--space-2);
  letter-spacing: -0.02em;
}

.notfound p {
  color: var(--color-text-muted);
  margin: 0 0 var(--space-4);
}

/* Mobile */
@media (max-width: 768px) {
  .hero {
    padding-top: var(--space-8);
    padding-bottom: var(--space-6);
  }

  .about,
  .projects {
    padding-top: var(--space-6);
    padding-bottom: var(--space-6);
  }

  section + section {
    margin-top: var(--space-6);
  }

  .nav {
    gap: var(--space-2);
    font-size: 0.9rem;
  }

  .footer-inner {
    flex-direction: column;
    align-items: flex-start;
  }
}