body{
    font-family: "Microsoft YaHei",sans-serif;
}

#container{
    min-width: 800px;
    min-height: 600px;
    position: fixed;
    left: 0px;
    top: 0px;
    width: 100%;
    height: 100%;
    display: flex;
    flex-flow: row wrap;
    justify-content: space-around;
    align-items: center;
}

.block{
    cursor: default;
    padding: 16px;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #f5f5f5;
    border: 2px #aaa solid;
    border-radius: 8px;
    transition: background-color 0.4s, color 0.4s;
}

.block:hover{
    background-color: #aaa;
    color: white;
}

#menu{
    background-color: white;
    border-radius: 4px;
    position: fixed;
    border: 2px #aaa solid;
    z-index: 999;
    left: -999px;
    top: -999px;
    transition: opacity 0.3s;
}

.menu-item{
    cursor: pointer;
    text-align: center;
    padding: 8px 24px 8px 24px;
    transition: color 0.3s;
}

.menu-item:hover{
    color: orange;
}

.hidden{
    opacity: 0;
}