/* quantumofgravity.com — clean academic style
 * Inspired by the minimalist personal-site tradition:
 * Paul Graham's essays, Bret Victor's worrydream.com,
 * and the Swiss-modernist approach to web typography.
 */

:root {
  --bg: #fafafa;
  --text: #1a1a1a;
  --text-light: #666;
  --accent: #2d5a8a;
  --accent-hover: #1e3d5c;
  --border: #e0e0e0;
  --card-bg: #fff;
  --font-body: 'Charter', 'Georgia', 'Times New Roman', serif;
  --font-sans: 'Inter', 'Helvetica Neue', Arial, sans-serif;
  --max-width: 720px;
}

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

body {
  font-family: var(--font-body);
  font-size: 1.1rem;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

/* Navigation */
nav {
  font-family: var(--font-sans);
  background: var(--card-bg);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 1.5rem;
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-brand {
  font-weight: 600;
  font-size: 1rem;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.01em;
}

.nav-brand:hover { color: var(--accent); }

.nav-links {
  display: flex;
  gap: 1.5rem;
  list-style: none;
  font-size: 0.9rem;
}

.nav-links a {
  color: var(--text-light);
  text-decoration: none;
  transition: color 0.2s;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--accent);
}

/* Layout */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

/* Hero / Intro */
.hero {
  padding: 3rem 0 2rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 2rem;
}

.hero h1 {
  font-family: var(--font-sans);
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.5rem;
  line-height: 1.2;
}

.hero .subtitle {
  font-size: 1.15rem;
  color: var(--text-light);
  font-style: italic;
  margin-bottom: 1rem;
}

.hero .tagline {
  font-size: 1rem;
  color: var(--text-light);
  max-width: 600px;
}

/* Sections */
section {
  margin-bottom: 2.5rem;
}

section h2 {
  font-family: var(--font-sans);
  font-size: 1.1rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-light);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

/* Cards / Links */
.link-card {
  display: block;
  padding: 1rem 0;
  border-bottom: 1px solid var(--border);
  text-decoration: none;
  color: var(--text);
  transition: padding-left 0.2s;
}

.link-card:last-child { border-bottom: none; }

.link-card:hover {
  padding-left: 0.5rem;
  color: var(--accent);
}

.link-card .title {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.25rem;
}

.link-card .desc {
  font-size: 0.95rem;
  color: var(--text-light);
  line-height: 1.5;
}

/* CJP Specifics */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.topic-card {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1.25rem;
  transition: box-shadow 0.2s, border-color 0.2s;
}

.topic-card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.06);
  border-color: var(--accent);
}

.topic-card .icon {
  font-size: 1.5rem;
  margin-bottom: 0.5rem;
}

.topic-card h3 {
  font-family: var(--font-sans);
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
}

.topic-card p {
  font-size: 0.9rem;
  color: var(--text-light);
  line-height: 1.5;
}

.topic-card .btn {
  display: inline-block;
  margin-top: 0.75rem;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--accent);
  text-decoration: none;
  padding: 0.4rem 0.8rem;
  border: 1px solid var(--accent);
  border-radius: 4px;
  transition: all 0.2s;
}

.topic-card .btn:hover {
  background: var(--accent);
  color: #fff;
}

/* Procedure steps */
.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.step {
  background: var(--card-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1rem;
}

.step h4 {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
  color: var(--accent);
}

.step p {
  font-size: 0.9rem;
  color: var(--text-light);
}

/* Syllabus list */
.syllabus-list {
  list-style: none;
}

.syllabus-list li {
  padding: 0.75rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 1rem;
}

.syllabus-list li:last-child { border-bottom: none; }

/* Footer */
footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-light);
  font-family: var(--font-sans);
  margin-top: 3rem;
}

/* Utilities */
.back-link {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  color: var(--text-light);
  text-decoration: none;
  margin-bottom: 1rem;
}

.back-link:hover { color: var(--accent); }

.tag {
  display: inline-block;
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-light);
  background: #f0f0f0;
  padding: 0.2rem 0.5rem;
  border-radius: 3px;
  margin-right: 0.4rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.note {
  background: #f8f9fa;
  border-left: 3px solid var(--accent);
  padding: 1rem;
  margin: 1rem 0;
  font-size: 0.95rem;
  color: var(--text-light);
}

/* Mobile */
@media (max-width: 600px) {
  .nav-container { flex-direction: column; gap: 0.5rem; }
  .nav-links { gap: 1rem; }
  .hero h1 { font-size: 1.6rem; }
  .topic-grid { grid-template-columns: 1fr; }
  .steps { grid-template-columns: 1fr; }
}