:root {
    --primary-color: #222222;
    --secondary-color: #1e88e5;
    --background-light: #f4f4f4;
    --background-dark: #2c2c2c;
    --text-light: #333;
    --text-dark: #f0f0f0;
    --glass-bg: rgba(255, 255, 255, 0.2);
    --glass-border: rgba(255, 255, 255, 0.3);
    --transition-speed: 0.3s;
}

/* General Styles */
body {
    font-family: 'Roboto', Arial, sans-serif;
    display: flex;
    flex-direction: column;
    align-items: center;
    height: 100vh;
    margin: 0;
    background: #2a2a2a;
    color: #f0f0f0;
    text-align: center;
    overflow: hidden;
    overflow-y: auto;
}

header {
    text-align: center;
    padding: 50px 20px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
    position: relative;
    z-index: 2;
    font-size: 3rem;
    margin-bottom: 10px;
    letter-spacing: 2px;
    font-size: 1.5rem;
}

.back-btn {
    position: absolute;
    top: 20px;
    left: 20px;
    color: var(--text-color);
    font-size: 1.2rem;
    text-decoration: none;
    background-color: transparent;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    transition: color var(--transition-speed);
}

.back-btn i {
    margin-right: 8px;
}

.back-btn:hover {
    color: var(--secondary-color);
}

h1 {
    font-size: 4rem;
    font-weight: bold;
    margin-bottom: 30px;
    text-transform: uppercase;
    letter-spacing: 2px;
    background: linear-gradient(45deg, #909090, #1e88e5);
    -webkit-background-clip: text;
    color: transparent;
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.05);
    }
    100% {
        transform: scale(1);
    }
}

/* Container for OS options */
.os-options {
    display: flex;
    gap: 20px;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    margin-top: 50px;
}

/* OS Card Styles (smaller buttons) */
.os-card {
    background: #333;
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease, transform 0.2s ease;
    width: 150px;
    min-height: 150px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
    backdrop-filter: blur(8px);
    border: 2px solid transparent;
}

.os-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.3);
    background: #424242;
    border-color: #607d8b;
}

.os-card img {
    width: 100px;
    margin-bottom: 15px;
    transition: transform 0.2s ease, filter 0.3s ease;
}

.os-card:hover img {
    transform: scale(1.1);
}

.os-card h3 {
    font-size: 1.2rem;
    font-weight: bold;
    color: #f0f0f0;
    margin-top: 10px;
    letter-spacing: 1px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .os-options {
        flex-direction: column;
    }

    .os-card {
        width: 180px;
        min-height: 180px;
    }
}

/* Footer Styles */
footer {
    width: 100%;
    padding: 10px 0;
    font-size: 1rem;
    color: #f0f0f0;
    text-align: center;
    margin-top: auto; /* This pushes the footer to the bottom */
}