:root {
    --bg-color: #f0f2f5;
    --container-bg: white;
    --text-color: #333;
    --ball-bg: #e0e0e0;
    --nav-btn-color: #555;
    --nav-btn-border: #ccc;
    --shadow-color: rgba(0,0,0,0.1);
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --container-bg: #2d2d2d;
    --text-color: #f0f0f0;
    --ball-bg: #444;
    --nav-btn-color: #aaa;
    --nav-btn-border: #555;
    --shadow-color: rgba(0,0,0,0.5);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    position: relative;
    transition: background-color 0.3s ease;
}

.top-nav {
    position: absolute;
    top: 20px;
    right: 20px;
    display: flex;
    gap: 10px;
}

.nav-btn {
    padding: 8px 20px;
    font-size: 0.9rem;
    background-color: transparent;
    color: var(--nav-btn-color);
    border: 2px solid var(--nav-btn-border);
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: none;
}

.nav-btn:hover {
    background-color: var(--nav-btn-color);
    color: var(--container-bg);
    border-color: var(--nav-btn-color);
}

.container {
    background-color: var(--container-bg);
    padding: 2rem;
    border-radius: 20px;
    box-shadow: 0 10px 25px var(--shadow-color);
    text-align: center;
    max-width: 500px;
    width: 90%;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

h1 {
    color: var(--text-color);
    margin-bottom: 2rem;
}

.numbers-container {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.ball {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: var(--ball-bg);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    font-weight: bold;
    color: var(--text-color);
    transition: all 0.3s ease;
    box-shadow: inset -3px -3px 5px rgba(0,0,0,0.1);
}

.ball.active {
    color: white;
    transform: scale(1.1);
}

/* Ball colors based on number ranges */
.range-1-10 { background-color: #fbc02d; } /* Yellow */
.range-11-20 { background-color: #1976d2; } /* Blue */
.range-21-30 { background-color: #d32f2f; } /* Red */
.range-31-40 { background-color: #7b1fa2; } /* Purple */
.range-41-45 { background-color: #388e3c; } /* Green */

button {
    padding: 12px 30px;
    font-size: 1.1rem;
    background-color: #4CAF50;
    color: white;
    border: none;
    border-radius: 50px;
    cursor: pointer;
    transition: background-color 0.3s, transform 0.1s;
    box-shadow: 0 4px 15px rgba(76, 175, 80, 0.3);
}

button:hover {
    background-color: #45a049;
}

button:active {
    transform: scale(0.98);
}