transform:rotate(45deg) 顺时针旋转45度

    1. <style>
    2.     div{
    3.         position: relative;
    4.         width: 240px;
    5.         height: 35px;
    6.         border: 1px solid green;
    7.     }
    8.     div::after{
    9.         content: "";
    10.         position: absolute;
    11.         top: 8px;
    12.         right: 15px;
    13.         width: 12px;
    14.         height: 12px;
    15.         border-right:1px solid green;
    16.         border-bottom: 1px solid green;
    17.         transform: rotate(45deg);
    18.         transition: all 0.2s;
    20.     }
    21.     div:hover::after{
    22.         transform: rotate(225deg);
    23.     }
    24. </style>
    25. <body>
    26.     <div></div>
    27. </body>

    image.pngimage.png