CSS拟物按钮

<div class="btn">F</div>

.btn {
        margin: 150px 0 0 150px;
        display: flex;
        justify-content: center;
        align-items: center;
        width: 100px;
        height: 100px;
        background-color: #fff;
        border-radius: 20px;
        font-size: 50px;
        color: #333;
        /* 禁止选中文本 */
        user-select: none;
        cursor: pointer;
        transition: all 0.4s ease-in-out;
        text-shadow: 2px 2px 2px #ccc;
        box-shadow: 20px 20px 30px rgba(0, 0, 0, 0.2), -20px -20px 30px rgba(225, 225, 225, 1);
        &:hover {
            font-size: 48px;
            box-shadow: 0 0 0 rgba(0, 0, 0, 0.2), 0 0 0 rgba(225, 225, 225, 0.8), inset 10px 10px 20px rgba(0, 0, 0, 0.1), inset -10px -10px 20px rgba(225, 225, 225, 1);

        }
}