:root {
    --bg-color: #f0f2f5;
    --text-color: #333;
    --container-bg: #fff;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --button-bg: #007bff;
    --button-hover: #0056b3;
    --accent-color: #4CAF50;
}

body.dark-mode {
    --bg-color: #1a1a1a;
    --text-color: #f0f2f5;
    --container-bg: #2d2d2d;
    --shadow-color: rgba(0, 0, 0, 0.5);
    --button-bg: #375a7f;
    --button-hover: #2b4764;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 10px;
    box-shadow: 0 4px 8px var(--shadow-color);
    text-align: center;
    transition: background-color 0.3s, box-shadow 0.3s;
}

h1 {
    margin-bottom: 1.5rem;
    color: var(--text-color);
}

.numbers-container {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    margin-bottom: 1.5rem;
}

.number {
    width: 50px;
    height: 50px;
    background-color: var(--accent-color);
    color: white;
    font-size: 1.5rem;
    font-weight: bold;
    border-radius: 50%;
    margin: 5px;
    display: flex;
    justify-content: center;
    align-items: center;
    animation: pop-in 0.5s ease-out forwards;
}

button {
    background-color: var(--button-bg);
    color: white;
    border: none;
    padding: 1rem 2rem;
    border-radius: 5px;
    cursor: pointer;
    font-size: 1rem;
    transition: background-color 0.3s ease;
}

button:hover {
    background-color: var(--button-hover);
}

.theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
}

@keyframes pop-in {
    0% {
        transform: scale(0);
        opacity: 0;
    }
    100% {
        transform: scale(1);
        opacity: 1;
    }
}