:root {
  --color-bg: #ffffff;
  --color-surface: #f7f8fa;
  --color-text: #1a1d23;
  --color-muted: #5b6470;
  --color-primary: #2d5cf6;
  --color-primary-hover: #1f47c7;
  --color-border: #e3e6eb;
  --color-notice-bg: #fff4d6;
  --color-notice-border: #e0b400;
  --radius: 10px;
  --max-width: 1080px;
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 1rem;
  --space-4: 1.5rem;
  --space-5: 2.5rem;
  --space-6: 4rem;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang TC",
    "Microsoft JhengHei", "Noto Sans TC", Roboto, Helvetica, Arial, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #0f1115;
    --color-surface: #171a21;
    --color-text: #e8eaed;
    --color-muted: #9aa3af;
    --color-primary: #6b8cff;
    --color-primary-hover: #8aa4ff;
    --color-border: #2a2f3a;
    --color-notice-bg: #3a3417;
    --color-notice-border: #8a7300;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  -webkit-text-size-adjust: 100%;
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin-inline: auto;
  padding-inline: var(--space-4);
}

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

:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: 3px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--color-bg);
  padding: var(--space-2) var(--space-3);
  z-index: 100;
}
.skip-link:focus { left: var(--space-3); top: var(--space-3); }

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--color-border);
}
@media (prefers-color-scheme: dark) {
  .site-header { background: rgba(15, 17, 21, 0.92); }
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  min-height: 56px;
}

.brand {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-text);
  letter-spacing: 0.05em;
}

.site-nav ul {
  list-style: none;
  display: flex;
  gap: var(--space-4);
  margin: 0;
  padding: 0;
}
.site-nav a { color: var(--color-muted); font-weight: 500; }
.site-nav a:hover { color: var(--color-text); text-decoration: none; }

.lang-switch {
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-1) var(--space-3);
  color: var(--color-text);
  cursor: pointer;
  font: inherit;
}
.lang-switch:hover { border-color: var(--color-primary); }

.section { padding-block: var(--space-6); }
.section:nth-child(even) { background: var(--color-surface); }

.section-title {
  font-size: clamp(1.5rem, 3vw, 2rem);
  margin-top: 0;
  margin-bottom: var(--space-3);
}
.section-subtitle {
  color: var(--color-muted);
  margin-top: 0;
  margin-bottom: var(--space-5);
}

.hero { text-align: center; padding-block: var(--space-6); }
.hero-title {
  font-size: clamp(2rem, 5vw, 3.25rem);
  line-height: 1.2;
  margin-bottom: var(--space-3);
}
.hero-subtitle {
  font-size: clamp(1rem, 2vw, 1.25rem);
  color: var(--color-muted);
  margin-bottom: var(--space-5);
}

.btn {
  display: inline-block;
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius);
  font-weight: 600;
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  font: inherit;
  font-weight: 600;
}
.btn-primary {
  background: var(--color-primary);
  color: #fff;
}
.btn-primary:hover {
  background: var(--color-primary-hover);
  text-decoration: none;
}
.btn-ghost {
  background: transparent;
  color: var(--color-text);
  border-color: var(--color-border);
}
.btn-ghost:hover { border-color: var(--color-primary); text-decoration: none; }

.about-bio { max-width: 60ch; color: var(--color-muted); }

.project-list {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 280px), 1fr));
  gap: var(--space-4);
  padding: 0;
  margin: 0;
}
.project-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-4);
}
.section:nth-child(even) .project-card { background: var(--color-surface); }
.project-name { margin-top: 0; font-size: 1.25rem; }
.project-desc { color: var(--color-muted); }
.project-links {
  display: flex;
  gap: var(--space-2);
  margin-top: var(--space-3);
  flex-wrap: wrap;
}

.contact-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: var(--space-3);
}
.contact-list li {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  align-items: baseline;
}
.contact-label {
  color: var(--color-muted);
  min-width: 6em;
}

.site-footer {
  border-top: 1px solid var(--color-border);
  padding-block: var(--space-5);
  text-align: center;
}
.footer-copyright { margin-bottom: var(--space-1); }
.footer-built { color: var(--color-muted); font-size: 0.875rem; margin: 0; }

.mode-notice {
  position: fixed;
  left: 50%;
  bottom: var(--space-4);
  transform: translateX(-50%);
  background: var(--color-notice-bg);
  border: 1px solid var(--color-notice-border);
  border-radius: var(--radius);
  padding: var(--space-2) var(--space-4);
  max-width: calc(var(--max-width) - 2rem);
  z-index: 60;
  text-align: center;
}
.mode-notice p { margin: 0; font-size: 0.9rem; }
.mode-notice[hidden] { display: none; }

.error-page { display: grid; place-items: center; min-height: 100vh; }
.error-content { text-align: center; }
.error-code {
  font-size: clamp(4rem, 12vw, 8rem);
  line-height: 1;
  margin: 0;
  color: var(--color-primary);
}
.error-message { color: var(--color-muted); margin-bottom: var(--space-5); }

@media (max-width: 640px) {
  .header-inner { flex-wrap: wrap; }
  .site-nav ul { gap: var(--space-3); }
  .contact-label { min-width: 0; }
}