:root {
  --bg: #fff; --fg: #222; --accent: #0077ff; --card: #f2f2f2;
}
[data-theme="dark"] {
  --bg: #0e1117; --fg: #c9d1d9; --accent: #58a6ff; --card: #161b22;
}
* { box-sizing: border-box; margin: 0; padding: 0; font-family: 'Segoe UI', sans-serif; }
body { background: var(--bg); color: var(--fg); }
header { display: flex; justify-content: space-between; align-items: center; padding: 1rem 2rem; background: var(--bg); position: sticky; top: 0; }
.logo { font-size: 1.5rem; color: var(--accent); }
#mode-toggle { border: none; background: none; font-size: 1.2rem; cursor: pointer; color: var(--fg); }
.home-section { text-align: center; padding: 4rem 2rem; }
.profile-pic { width: 140px; height: 140px; border-radius: 50%; border: 4px solid var(--accent); margin-bottom: 1rem; }
.btn { background: var(--accent); color: #fff; padding: 0.6rem 1.2rem; border-radius: 25px; text-decoration: none; margin-top: 1rem; display: inline-block; }
.section { padding: 2rem; }
h2 { color: var(--accent); margin-bottom: 1rem; text-align: center; }
.cert-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 1rem; }
.cert-item { background: var(--card); padding: 1rem; border-radius: 12px; text-align: center; cursor: pointer; transition: transform 0.3s ease; }
.cert-item:hover { transform: scale(1.05); box-shadow: 0 4px 15px rgba(0,0,0,0.1); }
footer { padding: 2rem; background: var(--card); text-align: center; }
.social-icons { display: flex; justify-content: center; gap: 1rem; }
.social-icons img { width: 40px; cursor: pointer; transition: transform 0.2s; }
.social-icons img:hover { transform: scale(1.2); }
#back-to-top { display: none; }
.modal { display: none; position: fixed; top: 0; left: 0; width: 100vw; height: 100vh; background: rgba(0,0,0,0.8); justify-content: center; align-items: center; }
.modal img { max-width: 80vw; max-height: 80vh; border-radius: 8px; }
.close { position: absolute; top: 20px; right: 30px; color: #fff; font-size: 2rem; cursor: pointer; }