:root {
    --color-primary: #005eb8;
    --color-primary-hover: #1b74d6;
    --color-primary-pressed: #004a94;
    --color-primary-soft: rgba(0, 94, 184, 0.12);
    --color-primary-strong: rgba(0, 94, 184, 0.9);
    --color-background: #f3f7fc;
    --color-surface: #ffffff;
    --color-surface-elevated: rgba(255, 255, 255, 0.9);
    --color-border: rgba(0, 94, 184, 0.18);
    --color-neutral-soft: rgba(0, 0, 0, 0.08);
    --color-neutral-strong: rgba(0, 0, 0, 0.75);
    --color-text: #000000;
    --color-text-inverse: #ffffff;
    --font-primary: 'Univers', Arial, Helvetica, sans-serif;
    --radius-large: 16px;
    --radius-medium: 12px;
    --radius-small: 8px;
    --shadow-elevated: 0 14px 40px rgba(0, 94, 184, 0.16);
}

*, *::before, *::after {
    box-sizing: border-box;
}

body {
    font-family: var(--font-primary);
    background: linear-gradient(135deg, rgba(0, 94, 184, 0.08), rgba(0, 94, 184, 0.02));
    color: var(--color-text);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 24px;
}

main.quiz-container {
    background-color: var(--color-surface);
    border-radius: var(--radius-large);
    box-shadow: var(--shadow-elevated);
    width: 100%;
    max-width: 640px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.quiz-header {
    background: linear-gradient(120deg, var(--color-primary), var(--color-primary-pressed));
    color: var(--color-text-inverse);
    padding: 28px 32px;
}

.quiz-header h1 {
    margin: 0;
    font-size: 1.9rem;
    letter-spacing: 0.02em;
}

.quiz-subtitle {
    margin-top: 6px;
    font-size: 1rem;
    opacity: 0.92;
}

.quiz-body {
    padding: 32px;
    background-color: var(--color-surface);
}

.question-text {
    font-size: 1.2rem;
    font-weight: 600;
    margin: 0 0 24px;
}

.options-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    gap: 14px;
}

.option {
    background-color: var(--color-surface-elevated);
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-medium);
    padding: 18px 20px;
    cursor: pointer;
    transition: transform 0.16s ease, box-shadow 0.16s ease, border-color 0.16s ease;
    line-height: 1.4;
}

.option:hover,
.option:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 6px 18px var(--color-primary-soft);
    transform: translateY(-1px);
    background-color: rgba(0, 94, 184, 0.06);
}

.option.selected {
    border-color: var(--color-primary);
    background-color: rgba(0, 94, 184, 0.1);
    font-weight: 600;
}

.option.correct {
    border-color: var(--color-primary);
    background-color: var(--color-primary-soft);
    color: var(--color-primary);
}

.option.incorrect {
    border-color: var(--color-neutral-soft);
    background-color: rgba(0, 0, 0, 0.04);
    color: var(--color-neutral-strong);
}

#feedback {
    margin-top: 20px;
    padding: 16px 20px;
    border-radius: var(--radius-medium);
    border: 1px solid transparent;
    font-weight: 500;
    background-color: var(--color-primary-soft);
    color: var(--color-primary);
}

#feedback.incorrect {
    background-color: rgba(0, 0, 0, 0.05);
    border-color: var(--color-neutral-soft);
    color: var(--color-neutral-strong);
}

.quiz-footer {
    padding: 24px 32px 32px;
    display: flex;
    justify-content: flex-end;
    gap: 12px;
    background-color: var(--color-surface);
}

button {
    font-family: var(--font-primary);
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-small);
    padding: 14px 28px;
    border: none;
    cursor: pointer;
    transition: background-color 0.16s ease, transform 0.16s ease;
}

#submit-btn,
#restart-btn {
    background-color: var(--color-primary);
    color: var(--color-text-inverse);
}

#submit-btn:hover,
#restart-btn:hover {
    background-color: var(--color-primary-hover);
    transform: translateY(-1px);
}

#submit-btn:active,
#restart-btn:active {
    background-color: var(--color-primary-pressed);
    transform: translateY(1px);
}

#submit-btn:disabled {
    background-color: rgba(0, 0, 0, 0.2);
    color: var(--color-text-inverse);
    cursor: not-allowed;
    transform: none;
}

.quiz-results {
    padding: 32px;
    text-align: center;
}

.quiz-results h2 {
    font-size: 1.6rem;
    color: var(--color-primary);
    margin-bottom: 12px;
}

.quiz-results p {
    font-size: 1.1rem;
    margin: 0;
}

[hidden] {
    display: none !important;
}

@media (max-width: 600px) {
    body {
        padding: 16px;
    }

    main.quiz-container {
        border-radius: var(--radius-medium);
    }

    .quiz-header,
    .quiz-body,
    .quiz-footer,
    .quiz-results {
        padding: 24px;
    }

    .option {
        padding: 16px;
    }
}