style.css

body {
    text-align: center;
    display: grid;
    justify-items: center;
    counter-reset: question 0;
}

#exam-content label {
    display: block;
    width: 100%;
}

.question, #exam-content label {
    text-align: left;
    padding-top: 0.5em;
    padding-bottom: 0.5em;
}

input[type="radio"], input[type="checkbox"] {
    transform: scale(1.2);
}

.free .question.single::before {
    content: "（单选）";
}

.free .question.multi::before {
    content: "（多选）";
}

.classic .question.single::before, .endless .question.single::before {
    content: counter(question) ". （单选）";
    counter-increment: question;
}

.classic .question.multi::before, .endless .question.multi::before {
    content: counter(question) ". （多选）";
    counter-increment: question;
}

.correct {
    background-color: lightgreen;
}

.incorrect {
    background-color: lightcoral;
}

:not(.correct):not(.incorrect) > .hide-answer {
    display: none;
}

.option:hover {
    background-color: aliceblue;
}

/*仅在自由练习模式下显示“换一题”按钮*/
.classic ~ #change-question, .endless ~ #change-question {
    display: none;
}

/*仅在无尽模式下显示“重新开始”按钮*/
.free ~ #restart, .classic ~ #restart {
    display: none;
}