stylesheet.css

body {
    position: absolute;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    margin: 0;

    display: flex;
    justify-content: center;
    align-items: center;
}

span {
    display: inline-block;
}

#words {
    display: inline-block;

    position: relative;

    color: #222;
    font-family: 'Roboto Mono', 'Courier New', Courier, monospace;
    font-weight: bold;
    font-size: 20px;
    
    max-width: 40%;
    padding: 4px 8px;
    border: 1px solid #DDD;
    border-radius: 8px;
}

.letter.passed {
    opacity: 0.5;
}

.letter.failed, .space.letter.failed::after {
    color: #F44;
    border-color: #F44 !important;
}

.letter.incorrect {
    background: #F44;
    color: #DDD;
    opacity: 1;
}

#words .space {
    position: relative;
    color: #0000;
    padding: 0 2px;
}

#words .space::after {
    position: absolute;
    left: .1em;
    bottom: .2em;
    
    content: "";

    width: calc(100% - .4em);
    height: 1px;
    
    border: solid .1em #AAA;
    border-top-width: 0;
}

.caret::after {
    content: "";
    
    display: inline-block;

    position: absolute;
    top: 5%;
    left: -1px;

    width: 2px;
    height: 90%;
    background: #222;
}

.debug-term {
    position: fixed;
    top:0;
    right: calc(-400px + 8px);
    width: 400px;
    height: 100%;;

    background: #222;
    color: #DDD;
    font-family: 'Roboto Mono', Courier, monospace;
    font-size: 10px;
    overflow-y: scroll;
    transition: right .5s;
}

.debug-term:hover {
    right: 0;
}

.debug-term .toggle {
    position: sticky;
    top:  16px;
    left: 16px;
    background: #DDD;
    border: solid 1px #AAA;
    border-radius: 8px;
    width: 32px;
    height: 32px;
    margin: 16px;
    cursor: pointer;
}

.debug-term .entry {
    margin: 4px;
    padding: 8px;
    border-radius: 4px;
    border: solid #444 1px;
}