:root {
    --bg-color: #f9f9f9;
    --text-color: #333;
    --primary-color: #4c6ef5;
    --card-bg: #ffffff;
}
.dark-theme {
    --bg-color: #1e1e1e;
    --text-color: #f9f9f9;
    --primary-color: #4c6ef5;
    --card-bg: #2a2a2a;
}
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body {
    font-family: 'Segoe UI', sans-serif;
    line-height: 1.6;
    background-color: var(--bg-color);
    color: var(--text-color);
    padding: 20px;
    transition: background 0.3s, color 0.3s;
}
header {
    background-color: var(--primary-color);
    color: white;
    padding: 20px;
    text-align: center;
    border-radius: 12px;
}
header button {
    margin-top: 10px;
    padding: 8px 16px;
    border: none;
    background: white;
    color: var(--primary-color);
    font-weight: bold;
    border-radius: 8px;
    cursor: pointer;
}
main {
    max-width: 900px;
    margin: auto;
}
section {
    margin-top: 40px;
}
h2 {
    color: var(--primary-color);
    margin-bottom: 10px;
}
.cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-top: 20px;
}
.card {
    background: var(--card-bg);
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    transition: transform 0.2s;
}
.card:hover {
    transform: scale(1.03);
}
footer {
    margin-top: 50px;
    text-align: center;
    font-size: 0.9em;
    color: #777;
}
a {
    color: var(--primary-color);
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}