html,
body {
    display: contents;
    font-family: system-ui, Avenir, Helvetica, Arial, sans-serif;
}

.topbar {
    position: sticky;
    width: 100%;
    background-color: black;
    color: white;
    display: flex;
    margin: 0;
    height: 2.5rem;
}

.topbar > *
{
    padding-inline: 1rem;
    background-color: black;
    color: white;
    align-content: center;
}

button {
    border-inline: 1px solid gray;
    appearance: none;
    border-block: 0;
    cursor: pointer;
}

button:hover {
    background-color: gray;
}

.content {
    width: 100%;
    position: fixed;
    height: 100%;
    border: 0;
}