* {
    box-sizing: border-box;
    padding: 0;
    margin: 0;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background: url(/img/bg.jpg) no-repeat center center fixed;
    background-size: cover;
}

#nav {
    position: fixed; /* 将导航栏固定在顶部 */
    top: 0; /* 距离页面顶部为 0 */
    left: 50%; /* 居中对齐 */
    transform: translateX(-50%); /* 完全居中 */
    border: none;
    border-radius: 10em;
    display: flex;
    list-style: none;
    background: #f5f5f5;
    box-shadow: 20px 40px 40px #00000033;
    padding: 10px;
    z-index: 1000; /* 保证导航栏位于其他内容之上 */
}


#nav li a {
    position: relative;
    padding: 15px 50px;
    font: 500 24px '优设标题黑';
    border: none;
    outline: none;
    color: rgb(70, 100, 180);
    display: inline-block;
    text-decoration: none;
    z-index: 3;
}

.slide1,
.slide2 {
    position: absolute;
    display: inline-block;
    height: 60px;
    border-radius: 10em;
    transition: all 0.6s cubic-bezier(0.23, 1, 0.32, 1.05);
}

.slide1 {
    background-color: rgb(170, 190, 255);
    z-index: 2;
}

.slide2 {
    opacity: 0;
    background-color: rgba(170, 190, 255, .5);
    z-index: 1;
    box-shadow: 0 0 20px #ffffffaa inset;
}

.squeeze {
    transform: scale(0.9);
}