/* canvas图层 */
#stage {
    width: 480px;
    height: 320px;
    position: relative;
    border: 1px solid black
}

canvas {
    position: absolute;
}

#ui-layer {
    z-index: 3
}

#game-layer {
    z-index: 2
}

#background-layer {
    z-index: 1
}