:root {
    --bg-color: #f7f7f7;
    --container-bg: #fff;
    --text-color: #333;
    --button-bg: #007aff;
    --button-hover: #0056b3;
    --number-bg: #f0f0f0;
    --number-text: #333;
    --shadow: rgba(0, 0, 0, 0.1);
}

body.dark-mode {
    --bg-color: #1a1a1a;
    --container-bg: #2d2d2d;
    --text-color: #f0f0f0;
    --button-bg: #3391ff;
    --button-hover: #66a9ff;
    --number-bg: #444;
    --number-text: #fff;
    --shadow: rgba(0, 0, 0, 0.5);
}

html, body {
    height: 100%;
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background: var(--bg-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    transition: background-color 0.3s, color 0.3s;
}

.container {
    position: relative;
    text-align: center;
    padding: 40px;
    border-radius: 15px;
    background: var(--container-bg);
    box-shadow: 0 10px 30px var(--shadow);
    transition: background-color 0.3s, box-shadow 0.3s;
}

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

#generate {
    background-color: var(--button-bg);
    color: white;
    border: none;
    padding: 15px 30px;
    font-size: 1.2em;
    border-radius: 10px;
    cursor: pointer;
    transition: background-color 0.3s, transform 0.2s;
    margin-bottom: 30px;
}

#generate:hover {
    background-color: var(--button-hover);
    transform: translateY(-2px);
}

.numbers-container {
    display: flex;
    justify-content: center;
    gap: 15px;
}

.number {
    width: 60px;
    height: 60px;
    background-color: var(--number-bg);
    color: var(--number-text);
    font-size: 1.8em;
    font-weight: bold;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    box-shadow: 0 4px 8px var(--shadow);
    transition: background-color 0.3s, color 0.3s, box-shadow 0.3s;
}

#theme-toggle {
    position: absolute;
    top: 15px;
    right: 15px;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: 5px;
    border-radius: 50%;
    transition: background-color 0.3s;
}

#theme-toggle:hover {
    background-color: rgba(128, 128, 128, 0.1);
}

/* Responsive Design */
@media (max-width: 600px) {
    .container {
        padding: 20px;
    }

    h1 {
        font-size: 2em;
    }

    #generate {
        padding: 12px 25px;
        font-size: 1.1em;
    }

    .number {
        width: 50px;
        height: 50px;
        font-size: 1.5em;
    }
}