<body> <h1 style="color: red">css實現矩形邊角加粗</h1> <div class="main"> <span></span> <span></span> <span></span> <span></span> </div> </body>
body{ display: flex; justify-content: center; flex-direction: column; align-items: center; } .main{ position: relative; width: 400px; height: 200px; border: 1px solid red; } .main span:nth-child(1){ position: absolute; left: -5px; top: -5px; padding: 15px; border-style: solid; border-color: rebeccapurple; border-width: 5px 0 0 5px; } .main span:nth-child(2){ position: absolute; right: -5px; top: -5px; padding: 15px; border-style: solid; border-color: rebeccapurple; border-width: 5px 5px 0 0; } .main span:nth-child(3){ position: absolute; right: -5px; bottom: -5px; padding: 15px; border-style: solid; border-color: rebeccapurple; border-width: 0 5px 5px 0; } .main span:nth-child(4){ position: absolute; left: -5px; bottom: -5px; padding: 15px; border-style: solid; border-color: rebeccapurple; border-width: 0 0 5px 5px; }