CSS display flex

order

<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
                box-sizing: border-box;
            }
            section {
                display: flex;
                flex-direction: column;
                text-align: center;
            }
            section img {
                order: -1
            }
        </style>
    </head>
    <body>
    	<section>
            <h2>countdown</h2>
            <img src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fuploads.xuexila.com%2Fallimg%2F1912%2F1135-191202143454.jpg&refer=http%3A%2F%2Fuploads.xuexila.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1639984107&t=eca951193e736a17eb96278117bcfb1f" width="100%">
            <article>The countdown to Christmas starts here.</article>
            <p><a href="#">more</a></p>
        </section>
    </body>
</html>

<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
                font-size: 12px;
                box-sizing: border-box;
            }
            nav ul {
                padding: 0.5rem;
                list-style: none;
                display: flex;
                flex-wrap: wrap;
            }
            nav ul li {
                margin: 0.2rem;
                flex: 1 0 auto;
                max-width: 10rem;
            }
            nav ul li a {
                position: relative;
                display: block;
                padding: 0.2rem 0.6rem;
                color: white;
                line-height: 1rem;
                background-color: black;
                border-radius: 0.2rem;
                text-decoration: none;
                text-align: center;
            }
            nav ul li a:before {
                position: absolute;
                content: '';
                width: 0;
                height: 0;
                border: 0.7rem solid transparent;
                border-right-width: 0.7rem;
                border-right-color: black;
                left: -1.2rem;
                top: 0;
            }
        </style>
    </head>
    <body>
    	<nav>
            <ul>
                <li><a href="">Fillithar</a></li>
                <li><a href="">Berzite</a></li>
                <li><a href="">Galidraan</a></li>
                <li><a href="">Gravlex Med</a></li>
                <li><a href="">Cato Neimoidia</a></li>
                <li><a href="">Coruscant</a></li>
                <li><a href="">Dantooine</a></li>
                <li><a href="">Dhandu</a></li>
                <li><a href="">Iktotchon</a></li>
                <li><a href="">Hosnian Prime</a></li>
                <li><a href="">Harkrova I</a></li>
                <li><a href="">Livno III</a></li>
                <li><a href="">Karfeddion</a></li>
                <li><a href="">Eriadu</a></li>
                <li><a href="">Jestefad</a></li>
                <li><a href="">Iridonia</a></li>
                <li><a href="">Malachor</a></li>
                <li><a href="">Gan Moradir</a></li>
                <li><a href="">Kethmandi</a></li>
                <li><a href="">Mirrin Prime</a></li>
                <li><a href="">Ezaraa</a></li>
                <li><a href="">Muunilinst</a></li>
                <li><a href="">Itapi Prime</a></li>
                <li><a href="">Nam Chorios</a></li>
            </ul>
        </nav>
    </body>
</html>

display - flex - 可伸缩项属性

<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
            }
            nav {
                width: 500px;
            }
            nav ul {
                display: flex;
                list-style: none;
            }
            nav ul li {
                flex: 1 0 0%;
            }
            nav ul li:nth-child(1){
                flex-grow: 2;
            }
        </style>
    </head>
    <body>
    	 <nav>
            <ul>
                <li>home</li>
                <li>spaceships</li>
                <li>planets</li>
                <li>stars</li>
            </ul>
        </nav>
    </body>
</html>

display-flex

<!DOCTYPE html>
<html>
    <head>
        <meta charset=utf-8>
        <style type="text/css">
            * {
                margin: 0;
                padding: 0;
                box-sizing: border-box;
            }
            nav ul {
                height: 2rem;
                list-style: none;
                display: flex;
                justify-content: center;
                align-items: center;
            }
            nav ul li {
                border: 1px solid black;
            }
            nav ul li:first-child {
                font-size: 1.2rem;
            }
        </style>
    </head>
    <body>
    	<nav>
            <ul>
                <li>home</li>
                <li>spaceships</li>
                <li>planets</li>
                <li>stars</li>
            </ul>
        </nav>
    </body>
</html>