:root {
    --bg-gradient: linear-gradient(to right top, #d16ba5, #c777b9, #ba83ca, #aa8fd8, #9a9ae1, #8aa7ec, #79b3f4, #69bff8, #52cffe, #41dfff, #46eefa, #5ffbf1);
    --container-bg: rgba(255, 255, 255, 0.8);
    --text-color: #1a1a1a;
    --number-bg: #fff;
    --number-text: #333;
    --btn-bg: #007bff;
    --btn-hover: #0056b3;
}

body.dark-mode {
    --bg-gradient: linear-gradient(to right top, #051937, #004d7a, #008793, #00bf72, #a8eb12);
    --container-bg: rgba(30, 30, 30, 0.9);
    --text-color: #f0f2f5;
    --number-bg: #2d2d2d;
    --number-text: #eee;
    --btn-bg: #3f51b5;
    --btn-hover: #303f9f;
}

body {
    font-family: 'Arial', sans-serif;
    background-color: #f0f2f5;
    color: var(--text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-image: var(--bg-gradient);
    transition: background-image 0.3s ease;
}

.container {
    position: relative;
    text-align: center;
    padding: 40px;
    background-color: var(--container-bg);
    border-radius: 15px;
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1), 0 6px 6px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    transition: background-color 0.3s ease;
}

#theme-toggle {
    position: absolute;
    top: 15px;
    right: 15px;
    padding: 8px 12px;
    font-size: 0.9em;
    cursor: pointer;
    background: transparent;
    border: 1px solid var(--text-color);
    color: var(--text-color);
    border-radius: 5px;
    transition: all 0.3s ease;
}

#theme-toggle:hover {
    background: var(--text-color);
    color: var(--container-bg);
}

h1 {
    margin-bottom: 30px;
    font-size: 2.5em;
    color: var(--text-color);
    text-shadow: 1px 1px 2px rgba(0,0,0,0.1);
}

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

.number {
    width: 60px;
    height: 60px;
    line-height: 60px;
    border-radius: 50%;
    background-color: var(--number-bg);
    font-size: 1.8em;
    font-weight: bold;
    color: var(--number-text);
    box-shadow: 0 4px 8px rgba(0,0,0,0.1);
    transition: transform 0.3s ease, background-color 0.3s ease, color 0.3s ease;
}

#generate-btn {
    padding: 15px 30px;
    font-size: 1.2em;
    color: #fff;
    background-color: var(--btn-bg);
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.3s ease, transform 0.2s ease;
    box-shadow: 0 4px 10px rgba(0, 123, 255, 0.3);
}

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

#generate-btn:active {
    transform: translateY(0);
}

/* Color classes for numbers - Slightly adjusted for dark mode visibility */
.color-1 { background-color: #fbc400; color: white; }
.color-10 { background-color: #69c8f2; color: white; }
.color-20 { background-color: #ff7272; color: white; }
.color-30 { background-color: #999; color: white; }
.color-40 { background-color: #b0d840; color: white; }