body {
    font-family: sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f0f0;
    transition: background-color 0.3s, color 0.3s;
}

body.dark {
    background-color: #1a1a2e;
    color: #e0e0e0;
}

body.dark .container {
    background-color: #16213e;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.5);
}

body.dark .number-display span {
    background-color: #0f3460;
    color: #e0e0e0;
}

body.dark #generate-btn {
    background-color: #e94560;
}

body.dark #generate-btn:hover {
    background-color: #c73652;
}

body.dark .history li {
    background-color: #0f3460;
    color: #e0e0e0;
}

.container {
    position: relative;
    text-align: center;
    background-color: white;
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s, box-shadow 0.3s;
}

.number-display {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin: 2rem 0;
}

.number-display span {
    display: inline-block;
    width: 50px;
    height: 50px;
    line-height: 50px;
    text-align: center;
    border-radius: 50%;
    background-color: #eee;
    font-size: 1.5rem;
    font-weight: bold;
}

#generate-btn {
    background-color: #4CAF50;
    color: white;
    padding: 1rem 2rem;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1rem;
    transition: background-color 0.3s;
}

#generate-btn:hover {
    background-color: #45a049;
}

.theme-toggle {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: none;
    border: 2px solid #ccc;
    border-radius: 20px;
    padding: 0.4rem 0.9rem;
    cursor: pointer;
    font-size: 0.85rem;
    transition: border-color 0.3s, color 0.3s, background-color 0.3s;
}

body.dark .theme-toggle {
    border-color: #e0e0e0;
    color: #e0e0e0;
}

.history ul {
    list-style: none;
    padding: 0;
}

.history li {
    margin: 0.5rem 0;
    background-color: #eee;
    padding: 0.5rem;
    border-radius: 5px;
}