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

.sidebar {
    position: fixed;
    top: 0;
    left: 0;
    min-height: 100%;
    width:80px;
    background-color: #151e3d;
    
    padding: 0.4rem 0.8rem;
    transition: all 0.5s ease;
    border-radius: 0px 10px 10px 0px;
}

.sidebar.active ~ .main-content{
    left: 250px;
    border-radius: 0px 30px 30px 0px;
    color: black;
}

.sidebar.active {
    width: 250px;
    color: white;
    border-radius: 0px 30px 30px 0px;
}

.sidebar a:link{
    color:seagreen;
}

.sidebar #btn {
    position: absolute;
    color: white;
    top: 2rem;
    left: 50%;
    font-size: 1.5rem;
    line-height: 50%;
    transform: translateX(-50%);
    cursor: pointer;
    
}

.sidebar.active #btn {
    left: 90%;
}

.sidebar .top .logo {
    color: white;
    display: flex;
    height: 50px;
    width: 100%;
    align-items: center;
    pointer-events: none;
    opacity: 0;
}

.sidebar.active .top .logo {
    opacity: 1;
}

.sidebar ul li {
    position: relative;
    list-style-type: none;
    color: seagreen;
    height: 50px;
    width: 90%;
    margin: 0.8rem auto;
    line-height: 50px;
}

.sidebar ul li a {
    color: white;
    display: flex;
    align-items: center;
    text-decoration: none;
    border-radius: 0.8rem;
}

.sidebar ul li a:hover {
    background-color: black;
    color: #151e3d;
}

.sidebar ul li a i {
    min-width: 50px;
    text-align: center;
    height: 50px;
    border-radius: 12px;
    line-height: 50px;
}

.sidebar .nav-item {
    opacity: 0;
}

.sidebar.active .nav-item {
    opacity: 1;
}

.sidebar ul li .tip {
    position: absolute;
    left: 125px;
    top: 50%;
    transform: translate(-50%, -50%);
    box-shadow: 0 0.5rem 0.8rem black;
    border-radius: .6rem;
    padding: .4rem 1.2rem;
    line-height: 1.8rem;
    z-index: 20;
    opacity: 0;
}

.sidebar ul li:hover .tip {
opacity: 1;
}

.sidebar.active ul li:hover .tip {
opacity: 0;
}

.main-content {
    position: relative;
    min-height: 100vh;
    top: 1rem;
    left: 80px;
    transition: all 0.5s ease;
    width: 95%;
    padding: 1rem;
}

ul {
    list-style-type: none;
}

ol {
    list-style-type: none;
}

.container {
display:flexbox;
justify-content: space-between;
}

html {
    background-color: whitesmoke;
}
header{
    text-align: center;
}
.introduction {
    text-align: center;
}

h1{
    text-align: center;
}