.ui-center {
    margin-top: 8vh;
}

/* Game Over Popup */
#game-over {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    display: none;
    justify-content: center;
    align-items: center;
}

#game-over-content {
    background: white;
    padding: 2vh 2vw;
    border-radius: 1vw;
    text-align: center;
}

#restart-btn {
    margin-top: 2vh;
    padding: 1vh 2vw;
    border: none;
    background: #007BFF;
    color: white;
    cursor: pointer;
    border-radius: 0.5vw;
    font-size: 1.8vw;
}

#restart-btn:hover {
    background: #0056b3;
}