:root {
    --primary-color: #3498db;
    --secondary-color: #2ecc71;
    --background-color: #111;
    --container-bg: #222;
    --text-color: #f0f2f5;
    --heading-color: #fff;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --number-text: #fff;
}

body.light-mode {
    --background-color: #f0f2f5;
    --container-bg: #fff;
    --text-color: #333;
    --heading-color: #333;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --number-text: #fff;
}

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

.container {
    background-color: var(--container-bg);
    padding: 40px;
    border-radius: 20px;
    box-shadow: 0 10px 30px var(--shadow-color);
    text-align: center;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

h1 {
    color: var(--heading-color);
    margin-bottom: 30px;
    font-size: 2.5rem;
    text-shadow: 0 0 10px rgba(255,255,255,0.1);
    transition: color 0.3s ease;
}

.numbers {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 40px;
}

.number {
    background-color: var(--primary-color);
    color: var(--number-text);
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.8rem;
    font-weight: bold;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    transition: transform 0.3s ease;
}

.number:hover {
    transform: scale(1.1);
}

.controls {
    display: flex;
    flex-direction: column;
    gap: 15px;
    align-items: center;
}

#generate {
    background-color: var(--secondary-color);
    color: #fff;
    border: none;
    padding: 15px 30px;
    border-radius: 10px;
    font-size: 1.2rem;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 0 10px rgba(46, 204, 113, 0.5);
}

#generate:hover {
    background-color: #27ae60;
    box-shadow: 0 0 20px rgba(46, 204, 113, 0.8);
    transform: translateY(-2px);
}

#theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    background: var(--container-bg);
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
    padding: 10px 20px;
    border-radius: 25px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s ease;
    z-index: 1000;
    box-shadow: 0 4px 15px var(--shadow-color);
}

#theme-toggle:hover {
    background-color: var(--primary-color);
    color: #fff;
}