/* --- Global Styles --- */
:root {
    /* Colors */
    --primary-color: #007bff; /* Blue */
    --secondary-color: #6c757d; /* Gray */
    --accent-color: #28a745; /* Green for correct answers */
    --danger-color: #dc3545; /* Red for incorrect answers/time warning */
    --light-bg: #f8f9fa; /* Very light gray */
    --dark-bg: #e9ecef; /* Slightly darker light gray */
    --text-color: #343a40; /* Dark gray text */
    --light-text-color: #ffffff; /* White text for dark backgrounds */
    --border-color: #dee2e6; /* Light border */
    --shadow-color: rgba(0, 0, 0, 0.1);

    /* Typography */
    --font-family-primary: 'Segoe UI', Arial, sans-serif;
    --font-size-base: 16px;
    --heading-font-weight: 700;

    /* Spacing */
    --spacing-xs: 5px;
    --spacing-sm: 10px;
    --spacing-md: 20px;
    --spacing-lg: 30px;
    --spacing-xl: 40px;

    /* Border Radius */
    --border-radius-sm: 5px;
    --border-radius-md: 8px;
    --border-radius-lg: 12px;

    /* Transitions */
    --transition-speed-fast: 0.2s;
    --transition-speed-normal: 0.3s;
}

body {
    font-family: var(--font-family-primary);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--light-bg);
    margin: 0;
    padding: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    overflow-x: hidden; /* Prevent horizontal scroll */
    -webkit-font-smoothing: antialiased; /* Smoother fonts on WebKit */
    -moz-osx-font-smoothing: grayscale; /* Smoother fonts on Firefox */
}

/* --- Layout Structure --- */
header.quiz-header {
    background-color: var(--primary-color);
    color: var(--light-text-color);
    padding: var(--spacing-md) var(--spacing-lg);
    text-align: center;
    box-shadow: 0 2px 8px var(--shadow-color);
    position: sticky;
    top: 0;
    z-index: 1000;
}

header.quiz-header h1 {
    margin: 0;
    font-size: 2.5em;
    font-weight: var(--heading-font-weight);
    letter-spacing: 0.5px;
}

main {
    flex: 1; /* Allows main content to grow and push footer down */
    display: flex; /* For centering sections */
    justify-content: center;
    align-items: center;
    padding: var(--spacing-md);
}

.quiz-container, .start-quiz-container, .results-container {
    background-color: var(--light-text-color);
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 15px var(--shadow-color);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    margin: var(--spacing-md) auto; /* Top/bottom margin, auto left/right */
    max-width: 800px;
    width: 90%;
    text-align: center;
    transition: transform var(--transition-speed-normal) ease-in-out, opacity var(--transition-speed-normal) ease-in-out;
}

/* Initial hidden state for transitions */
.quiz-container:not(.active), .start-quiz-container:not(.active), .results-container:not(.active) {
    opacity: 0;
    transform: translateY(20px);
}
.quiz-container.active, .start-quiz-container.active, .results-container.active {
    opacity: 1;
    transform: translateY(0);
}

/* --- Start Quiz Section --- */
.start-quiz-container h2 {
    font-size: 2em;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
    font-weight: var(--heading-font-weight);
}

.start-quiz-container p {
    font-size: 1.1em;
    margin-bottom: var(--spacing-lg);
}

/* --- Buttons --- */
.btn {
    padding: 12px 25px;
    border: none;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: 1.1em;
    font-weight: 600;
    transition: background-color var(--transition-speed-normal) ease,
                transform var(--transition-speed-fast) ease,
                box-shadow var(--transition-speed-fast) ease;
    outline: none; /* Remove default outline */
    margin: var(--spacing-xs); /* Space between buttons */
}

.btn:focus-visible { /* For accessibility with keyboard navigation */
    outline: 3px solid var(--primary-color);
    outline-offset: 3px;
}

.btn.primary-btn {
    background-color: var(--primary-color);
    color: var(--light-text-color);
}

.btn.primary-btn:hover:not(:disabled) {
    background-color: var(--primary-color);
    filter: brightness(115%); /* Slightly brighter on hover */
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(0,0,0,0.2);
}

.btn.secondary-btn {
    background-color: var(--secondary-color);
    color: var(--light-text-color);
}

.btn.secondary-btn:hover:not(:disabled) {
    background-color: var(--secondary-color);
    filter: brightness(115%);
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(0,0,0,0.2);
}

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
    box-shadow: none;
}

/* --- Quiz Info Bar (Header of Quiz Section) --- */
.quiz-info-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: var(--dark-bg);
    border-radius: var(--border-radius-md);
    margin-bottom: var(--spacing-lg);
    box-shadow: inset 0 1px 3px rgba(0,0,0,0.05);
}

.quiz-info-bar p {
    margin: 0;
    font-weight: 600;
    font-size: 1em;
}

#timer span {
    transition: color 0.3s ease;
}

.progress-wrapper {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    flex-grow: 1; /* Allow progress bar to take available space */
    margin: 0 var(--spacing-md);
}

#progress-bar {
    flex-grow: 1;
    height: 10px;
    background-color: var(--border-color);
    border: none;
    border-radius: 5px;
    overflow: hidden;
    margin: 0;
}

/* Progress bar fill color for WebKit (Chrome, Safari) */
#progress-bar::-webkit-progress-value {
    background-color: var(--primary-color);
    transition: width var(--transition-speed-normal) ease;
}
/* Progress bar background for WebKit */
#progress-bar::-webkit-progress-bar {
    background-color: var(--border-color);
}

/* Progress bar fill color for Firefox */
#progress-bar::-moz-progress-bar {
    background-color: var(--primary-color);
    transition: width var(--transition-speed-normal) ease;
}

/* --- Question Area --- */
.question-area {
    margin-bottom: var(--spacing-lg);
}

#current-question {
    font-size: 1.6em;
    margin-top: 0;
    margin-bottom: var(--spacing-lg);
    color: var(--text-color);
    font-weight: var(--heading-font-weight);
}

.options-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid; /* Use grid for options */
    grid-template-columns: 1fr; /* Default to single column */
    gap: var(--spacing-sm);
    text-align: left;
}

.option-item {
    background-color: var(--light-bg);
    padding: var(--spacing-sm) var(--spacing-md);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: 1.1em;
    transition: background-color var(--transition-speed-fast) ease,
                border-color var(--transition-speed-fast) ease,
                transform var(--transition-speed-fast) ease,
                box-shadow var(--transition-speed-fast) ease;
    outline: none; /* Remove default outline */
    display: flex;
    align-items: center;
    min-height: 48px; /* Ensure minimum touch target size */
}

.option-item:hover:not(.correct):not(.incorrect):not(.incorrect-unselected) {
    background-color: var(--dark-bg);
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.option-item:focus-visible {
    outline: 3px solid var(--primary-color);
    outline-offset: 3px;
}

/* Styles for answered options */
.options-list.answered .option-item {
    cursor: default; /* Change cursor after answered */
}

.option-item.correct {
    background-color: var(--accent-color);
    color: var(--light-text-color);
    border-color: var(--accent-color);
    font-weight: 600;
    box-shadow: 0 2px 10px rgba(40, 167, 69, 0.4);
    transform: scale(1.02);
}

.option-item.incorrect {
    background-color: var(--danger-color);
    color: var(--light-text-color);
    border-color: var(--danger-color);
    font-weight: 600;
    box-shadow: 0 2px 10px rgba(220, 53, 69, 0.4);
    transform: scale(1.02);
}

.option-item.incorrect-unselected {
    opacity: 0.6;
    background-color: var(--light-bg);
    border-color: var(--border-color);
    color: var(--secondary-color);
    transform: none;
    box-shadow: none;
}

/* --- Feedback and Hint --- */
.feedback-message {
    font-size: 1.15em;
    font-weight: 600;
    margin-top: var(--spacing-md);
    min-height: 1.5em; /* Reserve space to prevent layout shift */
}

.feedback-message.correct-feedback {
    color: var(--accent-color);
}

.feedback-message.incorrect-feedback {
    color: var(--danger-color);
}

.hint-display {
    background-color: var(--dark-bg);
    border: 1px dashed var(--secondary-color);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--border-radius-sm);
    margin-top: var(--spacing-md);
    font-style: italic;
    color: var(--secondary-color);
    text-align: left;
    max-width: 80%; /* Don't stretch too wide */
    margin-left: auto;
    margin-right: auto;
    animation: fadeIn var(--transition-speed-normal) ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* --- Quiz Actions (Buttons) --- */
.quiz-actions {
    display: flex;
    justify-content: flex-end; /* Align buttons to the right */
    gap: var(--spacing-sm);
    margin-top: var(--spacing-lg);
}

#hint-btn {
    margin-right: auto; /* Push hint button to the left */
}

/* --- Results Section --- */
.results-container h2 {
    font-size: 2em;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
    font-weight: var(--heading-font-weight);
}

#final-score {
    font-size: 1.5em;
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
}

#final-score span {
    color: var(--primary-color);
    font-size: 1.2em; /* Emphasize score value */
}

.results-actions {
    margin-top: var(--spacing-lg);
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
}

/* --- Footer --- */
footer.quiz-footer {
    background-color: var(--dark-bg);
    color: var(--text-color);
    padding: var(--spacing-md) var(--spacing-lg);
    text-align: center;
    margin-top: auto; /* Push footer to the bottom */
    border-top: 1px solid var(--border-color);
}

footer.quiz-footer p {
    margin: var(--spacing-xs) 0;
    font-size: 0.9em;
}

.social-links {
    margin-top: var(--spacing-sm);
}

.social-links a {
    color: var(--secondary-color);
    font-size: 1.5em;
    margin: 0 var(--spacing-sm);
    transition: color var(--transition-speed-fast) ease, transform var(--transition-speed-fast) ease;
}

.social-links a:hover {
    color: var(--primary-color);
    transform: translateY(-2px) scale(1.1);
}

/* --- Utility Classes --- */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* --- Media Queries for Responsiveness --- */

/* Small devices (phones, max 576px) */
@media (max-width: 576px) {
    body {
        padding: var(--spacing-sm);
    }

    header.quiz-header h1 {
        font-size: 1.8em;
    }

    .quiz-container, .start-quiz-container, .results-container {
        padding: var(--spacing-md);
        margin: var(--spacing-md) var(--spacing-sm);
        width: auto; /* Allow padding to define width */
    }

    .start-quiz-container h2, .results-container h2 {
        font-size: 1.5em;
    }

    #current-question {
        font-size: 1.3em;
    }

    .quiz-info-bar {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-xs);
        padding: var(--spacing-sm);
    }

    .quiz-info-bar p {
        font-size: 0.9em;
    }

    .progress-wrapper {
        width: 100%;
        margin: var(--spacing-sm) 0;
    }

    .options-list {
        gap: var(--spacing-xs);
    }

    .option-item {
        font-size: 1em;
        padding: var(--spacing-sm);
    }

    .quiz-actions, .results-actions {
        flex-direction: column;
        gap: var(--spacing-sm);
        margin-top: var(--spacing-md);
    }

    .btn {
        width: 100%; /* Full width buttons */
        max-width: 300px; /* Limit button width */
        margin: var(--spacing-xs) auto;
        font-size: 1em;
    }

    #hint-btn {
        margin-right: auto; /* Keep hint button aligned */
        margin-left: auto;
    }

    .social-links a {
        font-size: 1.2em;
        margin: 0 var(--spacing-xs);
    }
}

/* Medium devices (tablets, 577px to 992px) */
@media (min-width: 577px) and (max-width: 992px) {
    .quiz-container, .start-quiz-container, .results-container {
        padding: var(--spacing-lg);
        width: 90%;
    }

    .quiz-info-bar {
        padding: var(--spacing-md);
    }

    .options-list {
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); /* 2 columns */
        gap: var(--spacing-md);
    }

    #current-question {
        font-size: 1.5em;
    }
}

/* Large devices (desktops, 993px and up) - adjusted max-width */
@media (min-width: 993px) {
    .quiz-container, .start-quiz-container, .results-container {
        padding: var(--spacing-xl);
        max-width: 900px; /* Wider for larger screens */
    }
    .options-list {
        grid-template-columns: repeat(2, 1fr); /* Two columns layout */
        gap: var(--spacing-md);
    }
}