SOURCE

<button class="button">Click Me</button>

.button{
    border: none;
    outline: none;
    padding: 20px;
    width: 150px;
    background-color: red;
    font-size: 26px;
    text-align: center;
    display: inline-block;
    color: #fff;
    border-radius: 8px;
    cursor: pointer;
    text-decoration: none;
    box-shadow: 0 9px #999;
    transition: all 0.2s;
}
/* 通过阴影盒按钮垂直方向上的位移来实现按钮特效，实际上并未有元素高度改变，只是阴影在变化 */

.button:hover{
    background-color: rgb(255, 120, 100);
}
.button:active{
    background-color: red;
    box-shadow: 0 5px red;
    transform: translateY(4px)
}