效果实现案例1-林七七

<div id="container">
    <div id="square">
        <div id="tip">已点div>
    div>
div>

 1 *{
 2     margin: 0;
 3     padding: 0;
 4 }
 5 #container {
 6     text-align: center;
 7 }
 8 #square {
 9     position: relative;
10     background-color: #DBEDFD;
11     width: 100px;
12     height: 100px;
13     margin: 50px auto;
14     overflow:hidden;
15 }
16 #tip {
17     height: 20%;
18     width: 80%;
19     position: absolute;
20     top: 10%;
21     right: -20%;
22     transform: rotate(45deg);
23     background-color: white;
24 }