:root {
    --forest: #1b4332;
    --leaf: #2d6a4f;
    --mint: #d8f3dc;
    --text: #2d3748;
    --white: #ffffff;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: 'Segoe UI', Tahoma, sans-serif; color: var(--text); line-height: 1.6; }

/* Navigation */
nav {
    display: flex; justify-content: space-between; align-items: center;
    padding: 1rem 10%; background: var(--white); position: sticky; top: 0;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05); z-index: 1000;
}
.logo { font-weight: 800; font-size: 1.4rem; color: var(--forest); }
.nav-links a { text-decoration: none; color: var(--text); margin-left: 20px; font-weight: 600; font-size: 0.95rem; }
.nav-btn { background: var(--forest); color: white !important; padding: 8px 15px; border-radius: 4px; }

/* Hero Section */
.hero {
    height: 75vh;
    /* Laboratory Background Visual */
    background: linear-gradient(rgba(27, 67, 50, 0.7), rgba(27, 67, 50, 0.7)), 
                url('https://images.unsplash.com/photo-1581093588401-fbb62a02f120?auto=format&fit=crop&q=80');
    background-size: cover; background-position: center; color: white;
    display: flex; flex-direction: column; justify-content: center; align-items: center; text-align: center; padding: 0 20px;
}
.hero h1 { font-size: clamp(1.8rem, 5vw, 3rem); margin-bottom: 1rem; max-width: 900px; }
.hero p { font-size: 1.2rem; max-width: 700px; opacity: 0.9; }

/* Buttons */
.btn { background: var(--leaf); color: white; padding: 12px 25px; border-radius: 5px; font-weight: bold; text-decoration: none; display: inline-block; transition: 0.3s; border: none; }
.btn:hover { background: var(--forest); transform: translateY(-2px); }
.btn-white { background: white; color: var(--forest); }

/* Layout Components */
section { padding: 5rem 10%; }
.container { max-width: 1100px; margin: 0 auto; }
.section-title { text-align: center; margin-bottom: 3rem; }
.section-title h2 { color: var(--forest); font-size: 2.2rem; }

/* Grids */
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 2rem; }
.card { padding: 2.5rem; background: #f9fbf9; border-radius: 8px; border-left: 5px solid var(--leaf); box-shadow: 0 4px 15px rgba(0,0,0,0.05); }

/* Footer */
footer { background: #1a1a1a; color: #cbd5e0; padding: 4rem 10% 2rem; }
.footer-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 3rem; margin-bottom: 3rem; }
.footer-bottom { border-top: 1px solid #333; padding-top: 2rem; text-align: center; font-size: 0.8rem; }

@media (max-width: 768px) { section { padding: 3rem 5%; } .hero h1 { font-size: 2.2rem; } }