**************一***************
<div style="display: flex; justify-content: space-between">
? ? ? ? <div style="width: 100px; height: 100px; background-color: red"/>
? ? ? ? <div style="width: 100px; height: 100px; background-color: green"/>
</div>
***************二*************
<div style="width: 100px; height: 100px; border: 1px solid red;margin-top: 20px;display: flex; justify-content: center; align-items: center">
? ? ? ? <div style="width: 20px; height: 20px; background-color: green"/>
</div>
***************三*************
<div style="width: 100px; height: 100px; border: 1px solid red;margin-top: 20px;display: flex; justify-content: center; align-items: center; flex-direction: column">
? ? ? ? <div style="width: 20px; height: 20px; background-color: green;margin-left: 5px;margin-top: 5px"/>
? ? ? ? <div style="width: 20px; height: 20px; background-color: green;margin-left: 5px;margin-top: 5px"/>
? ? ? ? <div style="width: 20px; height: 20px; background-color: green;margin-left: 5px;margin-top: 5px"/>
? ? ? ? <div style="width: 20px; height: 20px; background-color: green;margin-left: 5px;margin-top: 5px"/>
</div>
