:root {
    --background-color: #f0f0f0;
    --container-bg-color: #fff;
    --text-color: #333;
    --number-bg-color: #eee;
    --h1-color: #333;
    --btn-bg-color: #4CAF50;
    --btn-text-color: white;
    --btn-shadow-color: rgba(76, 175, 80, 0.7);
    --btn-hover-shadow-color: rgba(76, 175, 80, 1);
}

body.dark-mode {
    --background-color: #121212;
    --container-bg-color: #1e1e1e;
    --text-color: #f0f0f0;
    --number-bg-color: #333;
    --h1-color: #f0f0f0;
    --btn-bg-color: #5cb85c;
    --btn-shadow-color: rgba(92, 184, 92, 0.7);
    --btn-hover-shadow-color: rgba(92, 184, 92, 1);
}

body {
    font-family: 'Arial', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: var(--background-color);
    background-image: url("data:image/svg+xml,%3Csvg width='100' height='100' viewBox='0 0 100 100' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M11 18c3.866 0 7-3.134 7-7s-3.134-7-7-7-7 3.134-7 7 3.134 7 7 7zm48 25c3.866 0 7-3.134 7-7s-3.134-7-7-7-7 3.134-7 7 3.134 7 7 7zm-43-7c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zm63 31c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM34 90c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM91 88c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3zM12 60c1.657 0 3-1.343 3-3s-1.343-3-3-3-3 1.343-3 3 1.343 3 3 3z' fill='%239C92AC' fill-opacity='0.13' fill-rule='evenodd'/%3E%3C/svg%3E");
    transition: background-color 0.3s ease;
}

.theme-switch-wrapper {
    position: absolute;
    top: 20px;
    right: 20px;
}

.theme-switch {
    position: relative;
    display: inline-block;
    width: 60px;
    height: 34px;
}

.theme-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #ccc;
    transition: .4s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 26px;
    width: 26px;
    left: 4px;
    bottom: 4px;
    background-color: white;
    transition: .4s;
}

input:checked + .slider {
    background-color: #2196F3;
}

input:focus + .slider {
    box-shadow: 0 0 1px #2196F3;
}

input:checked + .slider:before {
    transform: translateX(26px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}

.container {
    text-align: center;
    background-color: var(--container-bg-color);
    padding: 40px;
    border-radius: 20px;
    box-shadow: 0 10px 20px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23);
    transition: background-color 0.3s ease;
}

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

.numbers-container {
    display: flex;
    justify-content: center;
    margin-bottom: 30px;
}

.number {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background-color: var(--number-bg-color);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.5em;
    font-weight: bold;
    margin: 0 10px;
    color: var(--text-color);
}

#generate-btn {
    background-color: var(--btn-bg-color);
    color: var(--btn-text-color);
    padding: 15px 32px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 16px;
    margin: 4px 2px;
    cursor: pointer;
    border-radius: 8px;
    border: none;
    box-shadow: 0 0 10px var(--btn-shadow-color);
    transition: box-shadow 0.3s ease-in-out, background-color 0.3s ease;
}

#generate-btn:hover {
    box-shadow: 0 0 20px var(--btn-hover-shadow-color);
}