/* Base */
:root {
  --w: 1000px;
  --fg: #1a1a1a;
  --muted: #666;
  --link: #0066cc;
  --accent: #7c3aed;
  --surface: #f8fafc;
  --border: #e2e8f0;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,0.1);
}

* { 
  box-sizing: border-box;
}

html { 
  scroll-behavior: smooth;
}

body { 
  margin: 0; 
  font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; 
  color: var(--fg);
  background: white;
  padding: 2rem;
}

a { 
  color: var(--link); 
  text-decoration: none; 
}

a:hover { 
  text-decoration: underline;
}

/* Navigation */
.nav { 
  display: flex; 
  gap: 2rem; 
  margin-bottom: 3rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
}

.nav .brand { 
  font-weight: 700; 
  margin-right: auto;
}

.nav a {
  font-weight: 500;
}

/* Main Content */
main { 
  max-width: var(--w); 
  margin: 0 auto;
}

section { 
  margin-bottom: 4rem;
}

/* Typography */
h1, h2 { 
  line-height: 1.2; 
  margin: 0 0 16px; 
}

h1 { 
  font-size: 3rem; 
  font-weight: 700;
}

h2 { 
  font-size: 2rem; 
  font-weight: 600;
  margin-bottom: 24px;
}

p.muted { 
  color: var(--muted); 
  margin-top: 0; 
}

.small { 
  font-size: 14px; 
  color: var(--muted); 
}

/* Hero Section */
#about {
  margin-bottom: 4rem;
}

#about h1 {
  font-size: 2.5rem;
  margin-bottom: 1rem;
}

#about p {
  font-size: 1.1rem;
  color: var(--muted);
  margin-bottom: 1.5rem;
}

/* Grid Layout */
.grid { 
  display: grid; 
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); 
  gap: 2rem;
}

/* Cards */
.card { 
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
}

.card:hover {
  box-shadow: var(--shadow);
}

/* Badges & Chips */
.badges { 
  display: flex; 
  gap: 0.5rem; 
  flex-wrap: wrap; 
  margin: 1rem 0;
}

.badge { 
  padding: 0.25rem 0.5rem;
  background: var(--surface);
  border-radius: 999px;
  font-size: 0.875rem;
}

.chips { 
  display: flex; 
  flex-wrap: wrap; 
  gap: 0.5rem; 
  margin: 1rem 0;
}

.chip { 
  padding: 0.5rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

/* Certificates */
.cert-grid { 
  display: grid; 
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); 
  gap: 2rem;
}

.cert-card { 
  text-align: center;
}

.cert-badge { 
  width: 80px; 
  height: 80px; 
  object-fit: contain; 
  margin: 1rem auto 0.5rem; 
  display: block;
}

.cert-title { 
  margin: 1rem 0 0.5rem;
  font-weight: 600;
}

/* Paper Meta */
.paper-meta { 
  color: var(--muted); 
  margin: 8px 0 12px;
  font-size: 14px;
}

/* Footer */
footer { 
  text-align: center; 
  color: var(--muted); 
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
}

/* Responsive Design */
@media (max-width: 768px) {
  body {
    padding: 1rem;
  }
  
  .nav {
    flex-direction: column;
    gap: 1rem;
  }
}