画菱形或者尖角

使用css的skew属性进行倾斜

#angle {
    width: 100px;
    height: 100px;
    box-shadow: -1px -1px 2px 2px rgba(0,0,0,0.15);
    transform: translate(50%, 50%) rotate(45deg) skew(-43deg, 10deg);
    border-top-left-radius: 3px;
}