index.css

body {
}

.data {
    display: none;
}

.deck {
    text-align: center;
}
.deck__next,
.deck__start {
    display: inline-block;
    width: 45%;
    height: 50px;
    margin: 5px 5px;
    border: 1px solid #ccc;
    box-sizing: border-box;
    background-color: #fff;
    font-size: 15px;
}
.deck__next {
    width: 90%;
}

.deck__next:hover,
.deck__start:hover {
    background-color: #eee;
}
.deck__results {
    height: 50px;
    line-height: 20px;
    font-size: 20px;
}

.card {
    display: inline-block;
    width: 400px;
    border: 1px solid #ddd;
}
.card__word {
    height: 100px;
    text-align: center;
    vertical-align: middle;
}
.card__word-inner {
    line-height: 30px;
    font-size: 30px;
    position: relative;
    transform: translateY(-50%);
    top: 50%;
}
.card__options {
    text-align: center;
}
.card__option {
    display: inline-block;
    width: 45%;
    min-height: 60px;
    margin: 5px 5px;
    border: 1px solid #ccc;
    box-sizing: border-box;
    background-color: #fff;
    vertical-align: top;
    font: 16px system-ui;
    padding: 2px 6px 3px;
}
.card__option:hover {
    background-color: #eee;
}
.card__option--correct,
.card__option--correct:hover {
    border: 5px solid green;
}
.card__option--selected,
.card__option--selected:hover {
    border: 5px solid red;
}