:root {
    --bg-color: #f5f7fa;
    --card-bg: #ffffff;
    --text-primary: #333333;
    --text-secondary: #666666;
    --header-bg: #1a237e;
    --footer-bg: #1a237e;
    --accent: #667eea;
    --accent-hover: #764ba2;
    --border-color: #e0e0e0;
    --shadow: rgba(0, 0, 0, 0.1);
    --header-overlay: rgba(26, 35, 126, 0.85);
}

[data-theme='dark'] {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --header-bg: #020617;
    --footer-bg: #020617;
    --accent: #38bdf8;
    --accent-hover: #7dd3fc;
    --border-color: #334155;
    --shadow: rgba(0, 0, 0, 0.3);
    --header-overlay: rgba(2, 6, 23, 0.9);
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-color);
    min-height: 100vh;
}

header {
    background: linear-gradient(var(--header-overlay), var(--header-overlay)), url('../images/gbr_atas.webp');
    background-color: var(--header-bg);
    background-size: cover;
    background-position: center;
    padding: 3rem 2rem;
    text-align: center;
    box-shadow: 0 4px 20px var(--shadow);
    color: white;
}

header h1 {
    color: white;
    font-size: 2.8rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

header p {
    color: rgba(255, 255, 255, 0.95);
    font-size: 1.2rem;
}

main {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 2rem;
}

.demo-category {
    background: var(--card-bg);
    border-radius: 10px;
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: 0 4px 6px var(--shadow);
}

.demo-category h2 {
    color: var(--accent);
    margin-bottom: 1.5rem;
    border-bottom: 3px solid var(--accent);
    padding-bottom: 0.5rem;
}

.demo-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 1.5rem;
}

.demo-card {
    border: 2px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    background: var(--card-bg);
    transition: transform 0.3s, box-shadow 0.3s;
}

.demo-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 6px 12px var(--shadow);
    border-color: var(--accent);
}

.demo-card h3 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.demo-card p {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    font-size: 0.9rem;
}

.btn {
    display: inline-block;
    background: var(--accent);
    color: white;
    padding: 0.5rem 1.5rem;
    text-decoration: none;
    border-radius: 5px;
    transition: background 0.3s;
}

.btn:hover {
    background: var(--accent-hover);
}

footer {
    text-align: center;
    padding: 2rem;
    background-color: var(--footer-bg);
    color: white;
    margin-top: 2rem;
}

footer p {
    margin: 5px 0;
    font-size: 1em;
}

footer a {
    color: #ffd93d;
    text-decoration: none;
    font-weight: bold;
    transition: all 0.3s;
}

footer a:hover {
    color: #fff;
    text-decoration: underline;
    transform: translateY(-2px);
}

footer a svg {
    transition: transform 0.3s;
}

footer a:hover svg {
    transform: scale(1.1);
}