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

:root {
  --fg: #1a1a1a;
  --fg-secondary: #555;
  --fg-muted: #999;
  --bg: #fafafa;
  --border: #e5e5e5;
  --accent: #1a1a1a;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial,
    "PingFang SC", "Noto Sans SC", sans-serif;
  color: var(--fg);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }

/* --- Nav --- */
nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(250, 250, 250, 0.8);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
nav .nav-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 960px;
  margin: 0 auto;
  padding: 1rem 1.5rem;
}
nav .logo {
  font-size: 1.05rem;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--fg);
}
nav .links { display: flex; gap: 2rem; }
nav .links a {
  font-size: 0.875rem;
  color: var(--fg-secondary);
  transition: color 0.2s;
}
nav .links a:hover { color: var(--fg); }

/* --- Hero --- */
.hero {
  max-width: 960px;
  margin: 0 auto;
  padding: 10rem 1.5rem 6rem;
}
.hero h1 {
  font-size: clamp(3.0rem, 7vw, 4.5rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
}
.hero p {
  margin-top: 1.5rem;
  font-size: 1.125rem;
  color: var(--fg-secondary);
  max-width: 520px;
  line-height: 1.7;
}
.hero .actions {
  margin-top: 2.5rem;
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}
.btn {
  display: inline-block;
  padding: 0.7rem 1.8rem;
  font-size: 0.9rem;
  font-weight: 500;
  border-radius: 6px;
  transition: background 0.2s, color 0.2s;
}
.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover { background: #333; }
.btn-secondary {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--fg-secondary);
}
.btn-secondary:hover {
  border-color: var(--fg-secondary);
  color: var(--fg);
}

/* --- Divider --- */
.divider {
  max-width: 960px;
  margin: 0 auto;
  border: none;
  border-top: 1px solid var(--border);
}

/* --- About --- */
.about {
  max-width: 960px;
  margin: 0 auto;
  padding: 5rem 1.5rem 0;
}
.about h2 {
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
}
.about p {
  font-size: 1rem;
  color: var(--fg-secondary);
  line-height: 1.8;
  max-width: 640px;
}

/* --- Features --- */
.features {
  max-width: 960px;
  margin: 0 auto;
  padding: 5rem 1.5rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 3rem;
}
.feature h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}
.feature p {
  font-size: 0.9rem;
  color: var(--fg-secondary);
  line-height: 1.65;
}

/* --- Page Header --- */
.page-header {
  max-width: 960px;
  margin: 0 auto;
  padding: 8rem 1.5rem 3rem;
}
.page-header h1 {
  font-size: clamp(2rem, 4vw, 2.8rem);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
}
.page-header p {
  margin-top: 0.75rem;
  font-size: 1.05rem;
  color: var(--fg-secondary);
}

/* --- Showcase Section --- */
.showcase {
  max-width: 960px;
  margin: 0 auto;
  padding: 4rem 1.5rem;
}
.showcase h2 {
  font-size: 1.3rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 2rem;
}

/* --- Course Cards --- */
.course-grid {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
}
.course-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  width: 180px;
  height: 260px;
  padding: 1.5rem 1.25rem;
  background: var(--fg);
  color: #fff;
  border-radius: 4px;
  transition: transform 0.2s, box-shadow 0.2s;
}
.course-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.12);
}
.course-code {
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.05em;
  opacity: 0.6;
}
.course-title {
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.4;
}
.course-tag {
  font-size: 0.7rem;
  opacity: 0.5;
  align-self: flex-start;
  border: 1px solid rgba(255, 255, 255, 0.3);
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
}

/* --- Project Cards --- */
.project-grid {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}
.project-card {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 2rem;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.project-card:hover {
  border-color: #ccc;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.06);
}
.project-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1rem;
}
.project-header h3 {
  font-size: 1.2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.project-label {
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--fg-muted);
  border: 1px solid var(--border);
  padding: 0.15rem 0.6rem;
  border-radius: 3px;
  white-space: nowrap;
}
.project-desc {
  font-size: 0.9rem;
  color: var(--fg-secondary);
  line-height: 1.7;
  max-width: 640px;
  margin-bottom: 1rem;
}
.project-highlights {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem 1.5rem;
  margin-bottom: 1.25rem;
}
.project-highlights li {
  font-size: 0.85rem;
  color: var(--fg-secondary);
  position: relative;
  padding-left: 0.9rem;
}
.project-highlights li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.55em;
  width: 4px;
  height: 4px;
  border-radius: 50%;
  background: var(--fg-muted);
}
.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}
.project-tags span {
  font-size: 0.75rem;
  color: var(--fg-muted);
  background: #f0f0f0;
  padding: 0.2rem 0.6rem;
  border-radius: 3px;
}

/* --- Footer --- */
footer {
  max-width: 960px;
  margin: 0 auto;
  padding: 3rem 1.5rem;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
footer span {
  font-size: 0.8rem;
  color: var(--fg-muted);
}
footer .footer-links { display: flex; gap: 1.5rem; }
footer .footer-links a {
  font-size: 0.8rem;
  color: var(--fg-muted);
  transition: color 0.2s;
}
footer .footer-links a:hover { color: var(--fg); }

@media (max-width: 600px) {
  nav .nav-inner { padding: 0.8rem 1rem; }
  nav .links { gap: 1.2rem; }
  .hero { padding: 7rem 1rem 4rem; }
  .about { padding: 3rem 1rem 0; }
  .features { padding: 3rem 1rem; gap: 2rem; }
  .page-header { padding: 6rem 1rem 2rem; }
  .showcase { padding: 3rem 1rem; }
  .course-card { width: 150px; height: 220px; padding: 1.2rem 1rem; }
  .project-card { padding: 1.5rem; }
  .project-highlights { flex-direction: column; gap: 0.4rem; }
  footer { padding: 2rem 1rem; }
}