/* ROOT & RESET */
:root {
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-serif: 'Merriweather', Georgia, serif;
    
    --color-bg: #ffffff;
    --color-text: #1a1a1a;
    --color-text-light: #555555;
    --color-primary: #000000;
    --color-accent: #0044cc; /* Academic blue */
    --color-bg-light: #f4f6f8;
    --color-border: #e0e0e0;
    
    --spacing-container: 1100px;
}

* { box-sizing: border-box; }
body { margin: 0; font-family: var(--font-sans); color: var(--color-text); line-height: 1.6; }

/* UTILS */
.container { max-width: var(--spacing-container); margin: 0 auto; padding: 0 20px; }
.section { padding: 80px 0; }
.bg-light { background-color: var(--color-bg-light); border-top: 1px solid var(--color-border); border-bottom: 1px solid var(--color-border); }
.mt-4 { margin-top: 2rem; }
.center-text { text-align: center; }

h1, h2, h3 { margin-top: 0; color: var(--color-primary); }
h1 { font-family: var(--font-serif); font-weight: 700; }
h2 { font-family: var(--font-sans); font-weight: 600; font-size: 2rem; margin-bottom: 2rem; }

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

/* BUTTONS */
.btn { display: inline-block; padding: 12px 24px; border-radius: 4px; font-weight: 500; text-decoration: none; transition: background 0.2s; }
.btn-primary { background: var(--color-primary); color: #fff; }
.btn-primary:hover { background: #333; text-decoration: none; }
.btn-secondary { background: transparent; border: 1px solid var(--color-border); color: var(--color-text); margin-left: 10px; }
.btn-secondary:hover { border-color: #999; text-decoration: none; }

/* HEADER */
.site-header { padding: 20px 0; border-bottom: 1px solid var(--color-border); position: sticky; top: 0; background: rgba(255,255,255,0.95); backdrop-filter: blur(5px); z-index: 100; }
.site-header .container { display: flex; justify-content: space-between; align-items: center; }
.logo { font-weight: 700; font-size: 1.25rem; color: var(--color-primary); letter-spacing: -0.5px; display: flex; align-items: center; gap: 8px; }
.logo-sub { font-weight: 400; color: var(--color-text-light); }
.site-nav { display: flex; gap: 24px; }
.site-nav a { color: var(--color-text-light); font-weight: 500; }
.site-nav a:hover { color: var(--color-primary); }

/* HERO */
.hero { padding: 100px 0 120px; text-align: center; max-width: 800px; margin: 0 auto; }
.hero-title { font-size: 3.5rem; line-height: 1.1; margin-bottom: 24px; letter-spacing: -1px; }
.hero-subtitle { font-size: 1.25rem; color: var(--color-text-light); margin-bottom: 40px; max-width: 600px; margin-left: auto; margin-right: auto; }

/* CARDS GRID */
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 40px; }
.card h3 { font-size: 1.2rem; margin-bottom: 12px; }
.card p { font-size: 0.95rem; color: var(--color-text-light); }

/* PAPER LIST */
.paper-list { max-width: 800px; margin: 0 auto; }
.paper-item { padding: 24px 0; border-bottom: 1px solid var(--color-border); }
.paper-item:last-child { border-bottom: none; }
.paper-meta { font-size: 0.85rem; text-transform: uppercase; letter-spacing: 0.5px; color: #777; display: block; margin-bottom: 8px; }
.paper-item h3 { font-family: var(--font-serif); font-size: 1.4rem; margin-bottom: 8px; }
.paper-item h3 a { color: var(--color-primary); }
.paper-item h3 a:hover { color: var(--color-accent); }
.paper-item p { margin: 0; color: var(--color-text-light); }

/* FOOTER */
.site-footer { padding: 60px 0; border-top: 1px solid var(--color-border); margin-top: auto; }
.footer-content { display: flex; justify-content: space-between; align-items: center; margin-bottom: 40px; }
.footer-links { display: flex; gap: 20px; }
.footer-legal { font-size: 0.85rem; color: #999; text-align: center; }

/* RESPONSIVE */
@media (max-width: 768px) {
    .hero-title { font-size: 2.5rem; }
    .site-nav { display: none; } /* Simplified for MVP */
}