悬浮板

html部分

<div class="container">
 <div class="square">
 </div>
</div>

css部分

*{
    margin: 0;
    padding: 0;
}
body{
    background-color: #111;
    height: 100vh;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

.container{
    display: flex;
    justify-content: center;
    align-items: center;

    max-width: 400px;
    flex-wrap: wrap;
}
.square{
    background-color: #1d1d1d;
    box-shadow: 0 0 2px #000;
    height: 16px;
    width: 16px;
    margin: 2px;
    transition: 2s ;
}
.square:hover{
    transition-duration: 0s;
}

js部分

// 获取dom
const container=document.querySelector(".container")

// 颜色数组
const colors=['#e74c3c','#8e44ad','#3498db','#e67e22','#2ecc71']

// 方块数量
const num=519;

// 生成方块并且绑定事件
for(let i=0;i<num;i++){
    const square=document.createElement("div")
    square.classList.add("square")
    square.addEventListener("mouseover",()=>{
        setColor(square)
    })
    square.addEventListener("mouseout",()=>{
        removeColor(square)
    })
    container.appendChild(square)
}

// 设置颜色
function setColor(dom){
    dom.style.backgroundColor=colors[Math.floor(Math.random()*colors.length)]
}
// 移除颜色
function removeColor(dom){
    dom.style.backgroundColor='#1d1d1d'
}

效果