body {
    margin: 0; 
    padding: 0; 
    background-color: #050a0a;
    font-family: Arial, sans-serif; 
    overflow: hidden;
    display: flex; 
    justify-content: center; 
    align-items: center; 
    height: 100vh;
}

#game-container { 
    position: relative; 
    box-shadow: 0 0 30px rgba(0, 255, 200, 0.2); 
}

#shop-ui {
    display: none; 
    position: absolute; 
    top: 0; 
    left: 0; 
    width: 100%; 
    height: 100%;
    background: rgba(0, 15, 15, 0.95); 
    flex-direction: column;
    justify-content: center; 
    align-items: center; 
    z-index: 10;
}

.shop-box {
    background: #0a2a2a; 
    padding: 40px; 
    border: 2px solid #00ffcc;
    border-radius: 12px; 
    text-align: center; 
    width: 450px; 
    color: #fff;
    box-shadow: 0 0 20px rgba(0, 255, 204, 0.3);
}

.shop-box h1 { 
    color: #00ffcc; 
    margin-top: 0; 
    font-size: 32px; 
    letter-spacing: 2px; 
}

.coins-display {
    display: flex; 
    align-items: center; 
    justify-content: center; 
    gap: 10px; 
    margin-bottom: 20px;
}

.btn {
    background: #004444; 
    color: #fff; 
    border: 1px solid #00ffcc;
    padding: 15px 20px; 
    margin: 10px; 
    cursor: pointer; 
    font-size: 18px;
    font-weight: bold; 
    border-radius: 8px; 
    width: 85%; 
    transition: 0.3s;
    text-transform: uppercase;
}

.btn:hover:not(:disabled) { 
    background: #00ffcc; 
    color: #000; 
    transform: scale(1.05); 
}

.btn:disabled { 
    background: #222; 
    border-color: #444; 
    color: #666; 
    cursor: not-allowed; 
}

.btn-next { 
    background: #00ffcc; 
    color: #000; 
    margin-top: 30px; 
}