:root {
    --bg-color: #f0f0f0;
    --bg-gradient-color: #e0e0e0;
    --container-bg-color: #fff;
    --text-color: #333;
    --button-bg-color: #007bff;
    --button-hover-bg-color: #0056b3;
    --number-bg-color: #28a745;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

[data-theme='dark'] {
    --bg-color: #222;
    --bg-gradient-color: #333;
    --container-bg-color: #444;
    --text-color: #f0f0f0;
    --button-bg-color: #0056b3;
    --button-hover-bg-color: #003d80;
    --number-bg-color: #1e7e34;
    --shadow-color: rgba(255, 255, 255, 0.1);
}

body {
    font-family: sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: var(--bg-color);
    background-image: radial-gradient(var(--bg-gradient-color) 1px, transparent 0);
    background-size: 20px 20px;
    transition: background-color 0.3s ease;
}

.container {
    position: relative;
    text-align: center;
    padding: 40px;
    background-color: var(--container-bg-color);
    border-radius: 20px;
    box-shadow: 0 10px 20px var(--shadow-color), 0 6px 6px var(--shadow-color);
    transition: background-color 0.3s ease;
}

h1 {
    font-size: 2.5em;
    color: var(--text-color);
    margin-bottom: 20px;
}

#generate {
    padding: 15px 30px;
    font-size: 1.2em;
    color: #fff;
    background-color: var(--button-bg-color);
    border: none;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 6px rgba(0, 123, 255, 0.3);
}

#generate:hover {
    background-color: var(--button-hover-bg-color);
    box-shadow: 0 6px 8px rgba(0, 123, 255, 0.4);
    transform: translateY(-2px);
}

#theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
}

#numbers-container {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-top: 30px;
}

.number {
    width: 60px;
    height: 60px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5em;
    color: #fff;
    background-color: var(--number-bg-color);
    border-radius: 50%;
    box-shadow: 0 4px 6px rgba(40, 167, 69, 0.3);
    transform: scale(0);
    animation: pop-in 0.5s ease-out forwards;
}

@keyframes pop-in {
    to {
        transform: scale(1);
    }
}