:root {
    --background-color-light: #f0f2f5;
    --container-background-light: white;
    --text-color-light: #333;
    --number-background-light: #eee;
    --button-background-light: #4CAF50;
    --button-text-light: white;

    --background-color-dark: #222;
    --container-background-dark: #333;
    --text-color-dark: #f0f2f5;
    --number-background-dark: #555;
    --button-background-dark: #555;
    --button-text-dark: #f0f2f5;
}

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

body.dark-mode {
    background-color: var(--background-color-dark);
    color: var(--text-color-dark);
}

.container {
    text-align: center;
    background-color: var(--container-background-light);
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    transition: background-color 0.3s;
}

body.dark-mode .container {
    background-color: var(--container-background-dark);
}

header h1 {
    color: var(--text-color-light);
    margin-bottom: 30px;
}

body.dark-mode header h1 {
    color: var(--text-color-dark);
}

.number-display {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-bottom: 30px;
}

.number-display span {
    display: inline-block;
    width: 50px;
    height: 50px;
    line-height: 50px;
    border-radius: 50%;
    background-color: var(--number-background-light);
    color: #333;
    font-size: 24px;
    font-weight: bold;
    transition: background-color 0.3s, color 0.3s;
}

body.dark-mode .number-display span {
    background-color: var(--number-background-dark);
    color: var(--text-color-dark);
}

#generate-btn {
    background-color: var(--button-background-light);
    color: var(--button-text-light);
    padding: 15px 30px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 16px;
    transition: background-color 0.3s;
}

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

#generate-btn:active {
    background-color: #3e8e41;
}

body.dark-mode #generate-btn {
    background-color: var(--button-background-dark);
    color: var(--button-text-dark);
}

#theme-toggle-btn {
    background-color: #777;
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    font-size: 14px;
    transition: background-color 0.3s;
    margin-bottom: 20px;
}

#theme-toggle-btn:hover {
    background-color: #666;
}