.container { top: 0; bottom: 0; left: 0; right: 0; } .default { background-color: rebeccapurple; } .opposite { background-color: lightgreen; } .sticky { display: flex; justify-content: center; align-items: center; } .sticky-content { background-color: pink; font-size: 1.5rem; height: 5rem; width: 10rem; } .flex-center { display: flex; justify-content: center; align-items: center; } button { font-size: 2rem; cursor: pointer; }