* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.tip {
    position: fixed;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    font-family: Arial, Helvetica, sans-serif;
    color: #666;
    font-size: 16px;
    z-index: 999;
}

#canvas {
    width: 100vw;
    height: 100vh;
    background-color: #f8f8f8;
    cursor: crosshair;
    position: relative;
}

.square {
    position: absolute;
    border-radius: 4px;
    cursor: pointer;
    transition: transform 0.1s;
}

.square:active {
    transform: scale(0.95);
}