.navbar {
    text-decoration: none;
}
/* https://stackoverflow.com/questions/5721904/make-body-fill-entire-screen */
html {
    margin: 0;
    height: 100%;
}
body {
    background-image: linear-gradient(45deg, mediumseagreen, lightskyblue);
    background-size: cover;
    margin: 0;
    height: 100%;
}
/* https://www.w3schools.com/css/css3_buttons.asp */
button {
    background-color: lightgray;
    border-color: black;
    border-width: 3px;
    font-size: large;
}
/* TODO: make content in <article> centered */
/* https://stackoverflow.com/questions/114543/how-can-i-horizontally-center-an-element */