body {
    margin: 0;
    padding: 0;
    color: rgba(255, 255, 255, 0.87);
    background-color: #000000;
}

#app {
    width: 100%;
    height: 100vh;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

#game-container {
    position: relative;
}

#fullscreen-btn {
    position: absolute;
    bottom: 16px;
    right: 16px;
    width: 40px;
    height: 40px;
    font-size: 24px;
    background: rgba(0, 0, 0, 0.5);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 6px;
    color: rgba(255, 255, 255, 0.7);
    cursor: pointer;
    transition: background 0.2s, color 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
}

#fullscreen-btn:hover {
    background: rgba(0, 0, 0, 0.7);
    color: rgba(255, 255, 255, 0.9);
}

#fullscreen-btn.hidden {
    display: none;
}