:root {
    --color-background-light: #f9f9fb;
    --color-text-default: #333333;
    --color-blue-dark: #2c3e50;
    --color-table-odd-row: #f4f6f8;
    --color-border-light: #ddd;
    --color-link-blue: #2980b9;
    --color-link-blue-hover: #1c5980;
    --color-green: #27ae60;
    --color-green-hover: #1e874b;
    --color-red: #e74c3c;
    --color-red-hover: #b93628;
    --color-gray-light: #666666;
    --color-gray-medium: #555555;
    --color-gray-dark: #34495e;
    --color-gray-darker: #444444;
    --color-border-gray: #ccc;
    --color-shadow-light: rgba(0, 0, 0, 0.1);
    --color-shadow-lighter: rgba(0, 0, 0, 0.08);
    --color-shadow-medium: rgba(0,0,0,0.1);
    --color-shadow-stronger: rgba(0,0,0,0.1);
    --color-gray-button-prev-bg: #bdc3c7;
    --color-gray-button-prev-bg-hover: #95a5a6;
    --color-white: white;
}

/* Body */
body {
    font-family: Arial, sans-serif;
    background-color: var(--color-background-light);
    color: var(--color-text-default);
    margin: 0;
    padding: 0;
    text-align: center;
}

/* Title */
#title {
    margin-top: 20px;
    font-size: 2.2rem;
    color: var(--color-blue-dark);
    margin-bottom: 15px;
    font-weight: 700;
}
/*Selection page:*/
#tableDiv {
    overflow-x: auto;
    margin: 20px auto;
    max-width: 95%;
    border-radius: 8px;
    background: var(--color-white);
    padding: 10px;
    box-shadow: 0 2px 8px var(--color-shadow-light);
}

#table {
    border-collapse: collapse;
    width: 100%;
}

.tableRow.oddRow {
    background-color: var(--color-table-odd-row);
}

.tableCell {
    padding: 10px;
    border: 1px solid var(--color-border-light);
    text-align: center;
}

.nextPageLink {
    color: var(--color-link-blue);
    text-decoration: none;
    font-weight: bold;
    transition: color 0.2s, background-color 0.2s;
    display: block;
    padding: 5px;
    border-radius: 4px;
}

.nextPageLink:hover {
    background-color: var(--color-link-blue);
    color: var(--color-white);
}

#checkboxDiv {
    margin: 20px;
    display: flex;
    justify-content: center;
    gap: 20px;
    font-size: 0.95rem;
}

#checkboxDiv input[type="checkbox"] {
    margin-right: 5px;
}

#quizButton {
    padding: 8px 16px;
    font-size: 1rem;
    background-color: var(--color-green);
    color: var(--color-white);
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s;
}

#quizButton:hover {
    background-color: var(--color-green-hover);
}

#backButtonDiv {
    margin: 20px;
}

#backButton {
    color: var(--color-red);
    font-weight: bold;
    text-decoration: none;
    border: 2px solid var(--color-red);
    padding: 6px 12px;
    border-radius: 4px;
    transition: all 0.2s;
}

#backButton:hover {
    background-color: var(--color-red);
    color: var(--color-white);
}

/* index page:*/

#indexDiv {
    max-width: 600px;
    margin: 60px auto;
    background-color: var(--color-white);
    padding: 30px 25px;
    border-radius: 8px;
    box-shadow: 0 2px 10px var(--color-shadow-lighter);
    text-align: center;
}

#mainTitle {
    font-size: 2.5rem;
    color: var(--color-blue-dark);
    margin-bottom: 10px;
    font-weight: 700;
}

#author {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-gray-light);
    margin-bottom: 25px;
}

#credits {
    font-size: 0.9rem;
    line-height: 1.4;
    color: var(--color-gray-medium);
    margin-bottom: 25px;
}

#openstaxLink,
#ccLink,
#cc-saLink {
    color: var(--color-link-blue);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.2s ease;
}

#openstaxLink:hover,
#ccLink:hover,
#cc-saLink:hover {
    color: var(--color-link-blue-hover);
    text-decoration: underline;
}

#textbooksLink {
    display: inline-block;
    padding: 10px 18px;
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-green);
    border: 2px solid var(--color-green);
    border-radius: 5px;
    text-decoration: none;
    transition: background-color 0.2s, color 0.2s;
}

#textbooksLink:hover {
    background-color: var(--color-green);
    color: var(--color-white);
}

/* question/quiz page: */
#pageDiv {
    max-width: 960px;
    margin: 50px auto 80px auto;
    padding: 20px 25px;
    background-color: var(--color-white);
    border-radius: 8px;
    box-shadow: 0 3px 15px var(--color-shadow-medium);
    text-align: center;
}

#scoreDiv {
    margin-bottom: 25px;
}

#score {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--color-green);
}

#questionBody {
    text-align: left;
    margin-bottom: 35px;
    justify-content: center;
}

.questionDiv {
    margin-bottom: 25px;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
    padding: 0 20px;
}

.subquestionBody {
    margin-bottom: 20px;
}

.questionTitle {
    font-size: 1.4rem;
    font-weight: 600;
    color: var(--color-gray-dark);
    margin-bottom: 8px;
}

.questionText {
    font-size: 1rem;
    color: var(--color-gray-medium);
    line-height: 1.5;
    margin-bottom: 15px;
    text-align: left; /* keep left aligned */
}

table.unnumbered {
    width: 100%;
    border-collapse: collapse;
    margin-top: 10px;
}

table.unnumbered td {
    border: 1px solid var(--color-border-light);
    padding: 8px 12px;
    text-align: left;
    font-size: 0.95rem;
    color: var(--color-gray-darker);
}

.inputDiv {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-top: 15px;
    align-items: center;
}

.inputBox.textInput {
    flex-grow: 1;
    padding: 8px 12px;
    font-size: 1rem;
    border: 1px solid var(--color-border-gray);
    border-radius: 5px;
    font-family: Arial, sans-serif;
    transition: border-color 0.2s ease;
    overflow: hidden;       /* hide scrollbar */
    min-height: 1em;      /* adjust starting height */
    resize: vertical;
}

.inputBox.textInput:focus {
    outline: none;
    border-color: var(--color-link-blue);
}

.submitButton {
    padding: 9px 20px;
    background-color: var(--color-green);
    color: var(--color-white);
    border: none;
    border-radius: 5px;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s ease;
    flex-shrink: 0;
}

.submitButton:hover {
    background-color: var(--color-green-hover);
}

.solutionBody {
    background-color: var(--color-table-odd-row);
    border-left: 5px solid var(--color-link-blue);
    padding: 15px 20px;
    margin-top: 25px;
    border-radius: 5px;
    color: var(--color-gray-dark);
    font-size: 0.95rem;
    line-height: 1.4;
}

.solutionBody h3 {
    margin-top: 0;
    margin-bottom: 10px;
    font-weight: 700;
    color: var(--color-link-blue);
}

#selectionDiv {
    display: flex;
    justify-content: center;
    max-width: 480px;
    margin: 0 auto 35px auto;
    gap: 15px;
}

#previousButton, #nextButton {
    padding: 10px 22px;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

#previousButton {
    background-color: var(--color-gray-button-prev-bg);
    color: var(--color-blue-dark);
}

#previousButton:hover {
    background-color: var(--color-gray-button-prev-bg-hover);
    color: var(--color-white);
}

#nextButton {
    background-color: var(--color-link-blue);
    color: var(--color-white);
}

#nextButton:hover {
    background-color: var(--color-link-blue-hover);
}

#backButtonDiv {
    text-align: center;
    margin-bottom: 50px;
}

#backButton {
    display: inline-block;
    padding: 10px 24px;
    font-weight: 600;
    color: var(--color-red);
    border: 2px solid var(--color-red);
    border-radius: 6px;
    text-decoration: none;
    transition: background-color 0.2s, color 0.2s;
}

#backButton:hover {
    background-color: var(--color-red);
    color: var(--color-white);
}

/* Results Button */
#resultsButton {
    padding: 10px 24px;
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-white);
    background-color: var(--color-green);
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

#resultsButton:hover {
    background-color: var(--color-green-hover);
}

#resultsForm {
    display: inline-flex;
    align-items: center;
}

.selfGradeBody {
    margin: 25px 0;
    display: flex;
    justify-content: center;
    gap: 20px;
}

.correctButton {
    padding: 10px 28px;
    background-color: var(--color-green);
    color: var(--color-white);
    border: none;
    border-radius: 6px;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.correctButton:hover {
    background-color: var(--color-green-hover);
}

.incorrectButton {
    padding: 10px 28px;
    background-color: var(--color-red);
    color: var(--color-white);
    border: none;
    border-radius: 6px;
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.incorrectButton:hover {
    background-color: var(--color-red-hover);
}

.results {
    font-size: 1.2rem;
    font-weight: 700;
    text-align: center;
    margin-top: 15px;
}

/* Results page */
#resultsTitle {
    text-align: center;
    font-size: 2.4rem;
    color: var(--color-blue-dark);
    margin-top: 40px;
    margin-bottom: 25px;
}

#resultsDiv {
    max-width: 500px;
    margin: 0 auto 40px auto;
    background-color: var(--color-white);
    padding: 20px 25px;
    border-radius: 8px;
    box-shadow: 0 3px 12px var(--color-shadow-medium);
    text-align: center;
}

.finalResults {
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--color-gray-dark);
}

#restartButton,
#resultsBackButton {
    display: inline-block;
    margin: 10px 15px;
    padding: 10px 22px;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

#restartButton {
    background-color: var(--color-green);
    color: var(--color-white);
}

#restartButton:hover {
    background-color: var(--color-green-hover);
}

#resultsBackButton {
    background-color: var(--color-link-blue);
    color: var(--color-white);
}

#resultsBackButton:hover {
    background-color: var(--color-link-blue-hover);
}

.answerDiv {
    margin-top: 20px;
}
/* multiple choice: */
.radioLabel {
    display: flex;
    align-items: center;
    font-size: 1rem;
    color: var(--color-gray-dark);
    cursor: pointer;
    padding: 8px 12px;
    border-radius: 5px;
    transition: background-color 0.2s ease;
}

.radioLabel:hover {
    background-color: var(--color-table-odd-row);
}

.radio {
    margin-left: 10px;
    margin-right: 0;
    transform: scale(1.1);
    cursor: pointer;
}

/* question tables: */
.questionText table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 12px;
    background-color: var(--color-white);
    font-size: 0.95rem;
}

.questionText td {
    border: 1px solid var(--color-border-light);
    padding: 8px 12px;
    text-align: center;
    color: var(--color-gray-darker);
}

.questionText tr:first-child td {
    font-weight: 600;
    color: var(--color-gray-dark);
}

.questionText tr:nth-child(even) td {
    background-color: var(--color-table-odd-row, #f9f9f9);
}

.questionText td mjx-container {
    display: inline-block;
    vertical-align: middle;
}

/* question images: */
.questionText img {
    display: block;
    max-width: 100%;
    height: auto;
    margin-left: auto;
    margin-right: auto;
}