不会做选择器控制元素生效

这不是告诉你设置啥属性了吗。按照要求写呗。这个时css最基础的了。遇到不会的百度一下就行。练习 id和类选择器。
你改一下颜色。我懒得用ps了

<!DOCTYPE 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>Document</title>
    <style>
        .box {
            width: 800px;
        }

        p {
            font-family: "宋体";
            font-size: 14px;
            line-height: 18px;
            text-align: center;
        }

        #title {
            text-decoration: underline;
            color: palevioletred;
            font-weight: 800;
            font-size: 18px;
        }

        #one {
            color: red;
        }

        #two {
            color: blue;
            text-indent: 2em;
            letter-spacing: 16px;
            width: 800px;
            /* 文字显示三个点 */
            text-overflow: ellipsis;
            /* 空白部分不换行 */
            white-space: nowrap;
            /* 超出部分隐藏 */
            overflow: hidden;

        }
        #three{
            color: green;
            font-weight: 800;
            font-style:italic
        }
        #last{
            color: purple;
            text-decoration:line-through;
        }
    </style>
</head>

<body>
    <div class="box">
        <p id="title">你若安好</p>
        <p id="one">
            一个人，一本书
        </p>
        <p id="two">花开花落00000000099999999999999999999999999999999999999999999999999999999999999999999999999900000000000000000000000000000000000000000000000000000000000000000000</p>
        <p id="three">时光轮回</p>
        <p id="last">77777</p>
    </div>

</body>

</html>