:root {
    --primary-color: #4a90e2;
    --background-color: #f0f4f8;
    --text-color: #333;
    --white: #fff;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --card-background: #fff;
}

[data-theme='dark'] {
    --primary-color: #64b5f6;
    --background-color: #1a1a2e;
    --text-color: #e0e0e0;
    --white: #fff;
    --shadow-color: rgba(0, 0, 0, 0.5);
    --card-background: #16213e;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    margin: 0;
    transition: background-color 0.3s ease, color 0.3s ease;
}

header {
    margin-bottom: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

#theme-toggle {
    padding: 0.5rem 1rem;
    border: none;
    border-radius: 20px;
    background-color: var(--primary-color);
    color: white;
    cursor: pointer;
    font-weight: bold;
    transition: transform 0.2s;
}

#theme-toggle:hover {
    transform: scale(1.05);
}

h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
    text-shadow: 1px 1px 2px var(--shadow-color);
}

main {
    display: flex;
    justify-content: center;
    align-items: center;
}