<style>
.up{width:0;height:0;border: 100px solid transparent;border-top: 100px solid red;/*红色*/
}
.down{width:0;height:0;border: 100px solid transparent;border-bottom: 100px solid blue;/*蓝色*/
}
.left{width:0;height:0;border: 100px solid transparent;border-left: 100px solid pink;/*黑色*/
}
.right{width:0;height:0;border: 100px solid transparent;border-right: 100px solid pink;/*黄色*/
}
</style><body><div class="up"></div><div class="down"></div><div class="left"></div><div class="right"></div>
</body>
实现效果
