html, body{
    height: 100%;
    margin:0;
    background-color: rgb(250,250,250);
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

header {
    position: fixed;
    width: 100%;
    height: 50px;
    background-color: white;
    border-bottom: 1px solid rgb(220,220,220);
    box-shadow: 0 0 10px rgba(0,0,0,0.075);
    display: flex;
    justify-content: center;
    align-items: center;
}   
h1{
    
    text-align: center;
    font-size: 40px;
    color: white;
    margin: 0;
}

nav{
    width: 70%;
}

nav a{
    margin: 0 10px;
    padding: 10px 5px;
    text-decoration: none;
    color: rgb(40, 40, 40);
}
main{
    height: calc(100%-51px);
    overflow-y: scroll;
}
.lien{
    color: white;
    background: linear-gradient(45deg, red,blue);
    padding: 20px;
    border-radius: 5px;
    text-decoration: none;
    text-transform: uppercase;
    transition: 0.2s;
}
.lien:hover{
    background: rgb(245,245,245);
    color: rgb(40,40,40);
    
}