css在怎么让盒子在底部排列


html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>stitle>
    <style>
        .center{
            position: relative;
            width: 400px;
            height: 600px;
            margin: 0 auto;
            margin-top: 100px;
        }

        .box{
            width: 100px;
            height: 100px;
        }

        .box1 {
            position: absolute;
            left: 0;
            bottom: 0;
            background-color: pink;
        }

        .box2 {
            position: absolute;
            left: 100;
            bottom: 0;
            background-color: darkorchid;
        }

        .box3 {
            position: absolute;
            left: 200;
            bottom: 0;
            background-color: darkcyan;
        }

        .box4 {
            position: absolute;
            left: 300;
            bottom: 0;
            background-color: sandybrown;
        }
    <style>
head>
<body>
    <div class="center">
        <div class="box1 box">div>
        <div class="box2 box">div>
        <div class="box3 box">div>
        <div class="box4 box">div>
    div>

body>
<html>

为什么重合了？

img

那几个.box 的left值后面加px