html, body {
    height: 100%;
    margin: 0; /* removes default white margin around the page */
}

#frame {
    width: 65vh;
    height: 40vh;
    border: solid 5px;
    background-color: white;
    border-color: black;

    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);

    display: flex
}

.blue-rectangle,
.red-rectangle {
    width: 33.33%;
    height: 100%;
}
.blue-rectangle {
    background-color: darkblue;
}

.red-rectangle {
    background-color: rgb(214, 8, 8);
    margin-left: auto;
}