1.效果：
2.代码：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <style type="text/css"> * { margin: 0; padding: 0; } #bo { /* 如果将宽高设为0，就可以形成一个有四个三角形的正方形 */ width: 100px; height: 100px; /* transparent：透明的 */ border: 100px solid transparent; border-top-color: deeppink; border-left-color: red; border-right-color: blue; border-bottom-color: black; } #box { width: 0px; height: 0px; border: 100px solid transparent; border-top-color: deeppink; border-left-color: deeppink; /*border-right-color: deeppink;*/ /*border-bottom-color: deeppink;*/ } </style> </head> <body> <div id="bo"></div> <br/> <div id="box"></div> </body> </html>