:root {
    /* Light Theme (Default) */
    --bg-color: #f4f4f9;
    --card-bg: #ffffff;
    --text-main: #333333;
    --text-sub: #666666;
    --accent: #2563eb;
    --border: #e0e0e0;
}

[data-theme="dark"] {
    /* Dark Theme */
    --bg-color: #121212;
    --card-bg: #1e1e1e;
    --text-main: #e0e0e0;
    --text-sub: #a0a0a0;
    --accent: #60a5fa;
    --border: #333333;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    transition: background-color 0.3s, color 0.3s;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    padding: 20px;
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 40px;
}

.logo {
    font-weight: bold;
    font-size: 1.5rem;
}

#theme-toggle {
    background: none;
    border: 1px solid var(--border);
    padding: 8px 12px;
    border-radius: 20px;
    cursor: pointer;
    font-size: 1.2rem;
    background-color: var(--card-bg);
}

/* Main Content */
main {
    flex: 1;
    max-width: 800px;
    margin: 0 auto;
    width: 100%;
}

h1 {
    font-size: 2rem;
    margin-bottom: 10px;
}

.subtitle {
    color: var(--text-sub);
    margin-bottom: 30px;
}

/* Link Grid */
.link-grid {
    display: grid;
    grid-template-columns: 1fr; /* Mobile: 1 column */
    gap: 15px;
}

/* Card Styling */
.card {
    background-color: var(--card-bg);
    padding: 20px;
    border-radius: 12px;
    text-decoration: none;
    color: inherit;
    border: 1px solid var(--border);
    display: block;
}

.card:hover {
    transform: translateY(-2px);
    border-color: var(--accent);
}

.card h2 {
    font-size: 1.1rem;
    margin-bottom: 5px;
    color: var(--accent);
}

.url {
    display: block;
    font-size: 0.8rem;
    color: var(--text-sub);
    margin-bottom: 10px;
    font-family: monospace;
}

.card p {
    font-size: 0.95rem;
    color: var(--text-main);
}

/* Footer */
footer {
    margin-top: 50px;
    text-align: center;
    border-top: 1px solid var(--border);
    padding-top: 20px;
}

footer nav a {
    color: var(--text-sub);
    text-decoration: none;
    margin: 0 10px;
    font-size: 0.9rem;
}

footer nav a:hover {
    color: var(--accent);
}

footer p {
    margin-top: 15px;
    color: var(--text-sub);
    font-size: 0.8rem;
}

/* Desktop styles */
@media (min-width: 768px) {
    .link-grid {
        grid-template-columns: repeat(2, 1fr); /* Desktop: 2 columns */
    }
}