:root {
    --bg-color: #f0f2f5;
    --bg-gradient-color: #d7d7d7;
    --container-bg-color: white;
    --text-color: #333;
    --header-color: #1a73e8;
    --box-shadow-color: rgba(0,0,0,0.1);
    --btn-bg-color: #1a73e8;
    --btn-hover-bg-color: #155ab6;
    --btn-shadow-color: rgba(26, 115, 232, 0.4);
    --btn-hover-shadow-color: rgba(26, 115, 232, 0.5);
    --toggle-bg: #ccc;
    --toggle-fg: white;
    --toggle-checked-bg: #1a73e8;
}

body.dark-mode {
    --bg-color: #121212;
    --bg-gradient-color: #333;
    --container-bg-color: #1e1e1e;
    --text-color: #f0f2f5;
    --header-color: #69c8f2;
    --box-shadow-color: rgba(255,255,255,0.1);
    --btn-bg-color: #69c8f2;
    --btn-hover-bg-color: #5aaad8;
    --btn-shadow-color: rgba(105, 200, 242, 0.4);
    --btn-hover-shadow-color: rgba(105, 200, 242, 0.5);
    --toggle-checked-bg: #69c8f2;
}

body {
    font-family: 'Helvetica Neue', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background: var(--bg-color);
    background-image: radial-gradient(var(--bg-gradient-color) 1px, transparent 0);
    background-size: 40px 40px;
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

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

.header {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 20px;
    margin-bottom: 30px;
}

h1 {
    margin: 0;
    font-size: 2.5em;
    color: var(--header-color);
}

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

.number {
    width: 60px;
    height: 60px;
    display: flex;
    justify-content: center;
    align-items: center;
    border-radius: 50%;
    font-size: 1.8em;
    font-weight: bold;
    color: white;
    box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    transition: transform 0.3s ease;
}

.number:hover {
    transform: translateY(-5px);
}

#generate-btn {
    padding: 15px 30px;
    font-size: 1.2em;
    border: none;
    border-radius: 8px;
    background-color: var(--btn-bg-color);
    color: white;
    cursor: pointer;
    transition: background-color 0.3s, box-shadow 0.3s;
    box-shadow: 0 4px 15px var(--btn-shadow-color);
}

#generate-btn:hover {
    background-color: var(--btn-hover-bg-color);
    box-shadow: 0 6px 20px var(--btn-hover-shadow-color);
}

/* Theme Switcher */
.theme-switcher {
    position: relative;
    display: inline-block;
    width: 60px;
    height: 34px;
}

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

.theme-switcher label {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--toggle-bg);
    transition: .4s;
    border-radius: 34px;
}

.theme-switcher label:before {
    position: absolute;
    content: "";
    height: 26px;
    width: 26px;
    left: 4px;
    bottom: 4px;
    background-color: var(--toggle-fg);
    transition: .4s;
    border-radius: 50%;
}

input:checked + label {
    background-color: var(--toggle-checked-bg);
}

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