<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Document</title> <style> * { margin: 0; padding: 0; } #box { width: 200px; height: 200px; background: #00f; } /* padding-top 百分比相当于视口的宽度 */ </style> </head> <body> <div id="box"></div> </body> </html>
