/* --- Variables for Theming --- */
:root {
    --bg-color: 244, 247, 246;
    --text-color: 51, 51, 51;
    --header-bg: 74, 144, 226;
    --header-text: 255, 255, 255;
    --card-bg: 255, 255, 255;
    --card-border: 224, 224, 224;
    --hover-color: 240, 240, 240;
    --button-bg-primary: 74, 144, 226;
    --button-text-primary: 255, 255, 255;
    --button-bg-secondary: 108, 117, 125;
    --button-text-secondary: 255, 255, 255;
    --accent-color: 26, 115, 232;
    --correct-answer: 212, 237, 218;
    --incorrect-answer: 248, 215, 218;
    --correct-text: 40, 167, 69;
    --incorrect-text: 220, 53, 69;
    --input-border: 206, 212, 218;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.05);
    --glass-border: rgba(255, 255, 255, 0.2);
}

body.dark-mode {
    --bg-color: 44, 44, 44;
    --text-color: 224, 224, 224;
    --header-bg: 26, 42, 64;
    --header-text: 255, 255, 255;
    --card-bg: 60, 60, 60;
    --card-border: 85, 85, 85;
    --hover-color: 68, 68, 68;
    --button-bg-primary: 92, 158, 255;
    --button-text-primary: 44, 44, 44;
    --button-bg-secondary: 126, 135, 144;
    --button-text-secondary: 255, 255, 255;
    --accent-color: 121, 191, 248;
    --correct-answer: 61, 106, 69;
    --incorrect-answer: 122, 58, 65;
    --correct-text: 139, 195, 74;
    --incorrect-text: 239, 83, 80;
    --input-border: 102, 102, 102;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
    --glass-border: rgba(0, 0, 0, 0.2);
}

/* --- Base Styles --- */
body {
    font-family: 'Inter', sans-serif;
    margin: 0;
    padding: 0;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    color: rgb(var(--text-color));
    transition: background 0.3s ease, color 0.3s ease;
    line-height: 1.6;
}

body.dark-mode {
    background: linear-gradient(135deg, #2c3e50 0%, #4ca1af 100%);
}

.container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 20px;
}

        /* --- Header & Navigation --- */
        .header {
            background-color: rgba(var(--header-bg), 0.8);
            backdrop-filter: blur(10px);
            color: rgb(var(--header-text));
            padding: 15px 0;
            box-shadow: var(--shadow);
            position: sticky;
            top: 0;
            z-index: 1000;
            border-bottom: 1px solid var(--glass-border);
        }

        .header .container {
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            padding: 20px; /* Ensure ample horizontal spacing */
        }

        .header h1 {
            margin: 0;
            font-size: 1.8em;
            flex-shrink: 0;
        }

        .header-right {
            display: flex;
            align-items: center;
            gap: 20px; /* Space between nav and theme-toggle */
        }

        .main-nav {
            display: flex;
            gap: 15px; /* Increased spacing between buttons */
        }

        .nav-button {
            background-color: transparent;
            border: 2px solid rgb(var(--header-text));
            color: rgb(var(--header-text));
            padding: 8px 15px;
            border-radius: 25px;
            cursor: pointer;
            font-size: 0.9em;
            font-weight: 600;
            transition: background-color 0.3s ease, color 0.3s ease, transform 0.2s ease;
        }

        .nav-button:hover {
            background-color: rgba(255, 255, 255, 0.1);
            transform: translateY(-2px);
        }

        .nav-button.active {
            background-color: rgb(var(--header-text));
            color: rgb(var(--header-bg));
            border-color: rgb(var(--header-text));
        }

        .nav-button:active {
            transform: translateY(1px);
        }

        .theme-toggle {
            display: flex;
            align-items: center;
        }

        /* Media Query for Responsive Design */
        @media (max-width: 768px) {
            .header .container {
                flex-direction: column;
                text-align: center;
            }

            .header-right {
                flex-direction: column;
                align-items: center;
                width: 100%;
                gap: 15px; /* Adjusted spacing for smaller screens */
            }

            .main-nav {
                flex-direction: column;
                width: 100%;
                gap: 5px; /* Tighter spacing between buttons when stacked */
            }

            .nav-button {
                width: 100%;
            }

            .theme-toggle {
                margin-top: 0; /* Reset any unwanted margins */
            }
        }

/* Theme Toggle */
.theme-toggle {
    margin-left: auto;
    display: flex;
    align-items: center;
    order: 3;
    flex-basis: 100%;
    justify-content: flex-end;
    margin-top: 10px;
}

@media (min-width: 768px) {
    .theme-toggle {
        flex-basis: auto;
        margin-top: 0;
    }
    .main-nav {
        margin: 0;
    }
}

.dark-mode-checkbox {
    width: 0;
    height: 0;
    visibility: hidden;
}

.dark-mode-label {
    width: 60px;
    height: 30px;
    background-color: rgba(17, 17, 17, 0.8);
    backdrop-filter: blur(5px);
    display: block;
    border-radius: 100px;
    position: relative;
    cursor: pointer;
    transition: background-color 0.3s ease;
    border: 1px solid var(--glass-border);
}

.dark-mode-label .ball {
    content: '';
    position: absolute;
    top: 2px;
    left: 2px;
    width: 26px;
    height: 26px;
    background-color: white;
    border-radius: 50%;
    transition: transform 0.3s linear;
}

.dark-mode-checkbox:checked + .dark-mode-label .ball {
    transform: translateX(30px);
}

.dark-mode-label i {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    font-size: 14px;
}

.dark-mode-label .fa-moon {
    left: 8px;
    color: #f1c40f;
}

.dark-mode-label .fa-sun {
    right: 8px;
    color: #f39c12;
}

.dark-mode-checkbox:checked + .dark-mode-label .fa-moon {
    display: none;
}

.dark-mode-checkbox:not(:checked) + .dark-mode-label .fa-sun {
    display: none;
}

/* --- Content Sections --- */
.content-section {
    display: none;
    padding: 20px 0;
}

.content-section.active {
    display: block;
}

.section-title {
    font-size: 2em;
    color: rgb(var(--accent-color));
    margin-bottom: 30px;
    text-align: center;
    border-bottom: 2px solid rgb(var(--card-border));
    padding-bottom: 15px;
    font-weight: 700;
}

/* --- Notes Section Styling (Collapsible Cards) --- */
.collapsible-card {
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    margin-bottom: 20px;
    box-shadow: var(--shadow);
    overflow: hidden;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 20px;
    background-color: transparent;
    cursor: pointer;
    border-bottom: 1px solid rgb(var(--card-border));
    transition: background-color 0.2s ease;
}

.collapsible-card.open .card-header {
    background-color: rgba(var(--hover-color), 0.5);
}

.card-header:hover {
    background-color: rgba(var(--hover-color), 0.5);
}

.topic-title {
    margin: 0;
    font-size: 1.3em;
    color: rgb(var(--text-color));
    font-weight: 600;
}

.arrow-icon {
    transition: transform 0.3s ease;
}

.collapsible-card.open .arrow-icon {
    transform: rotate(180deg);
}

.card-content {
    padding: 0 20px;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.5s ease-out, padding 0.5s ease-out, opacity 0.5s ease-out;
    opacity: 0;
}

.collapsible-card.open .card-content {
    max-height: 5000px; /* Increased greatly to accommodate longer content */
    padding: 20px;
    opacity: 1;
    overflow-y: auto; /* Allows vertical scrolling if content exceeds max-height */
}

.card-content h4 {
    color: rgb(var(--accent-color));
    margin-top: 20px;
    margin-bottom: 10px;
    border-bottom: 1px dashed rgb(var(--card-border));
    padding-bottom: 5px;
    font-weight: 600;
}

.card-content h4:first-of-type {
    margin-top: 0;
}

.card-content ul {
    list-style: disc;
    padding-left: 25px;
    margin-bottom: 15px;
}

.card-content ol {
    list-style: decimal;
    padding-left: 25px;
    margin-bottom: 15px;
}

.card-content li {
    margin-bottom: 8px;
}

.card-content strong {
    color: rgb(var(--text-color));
    font-weight: 700;
}

/* --- Quiz Section Styling --- */

#quiz-settings {
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    padding: 25px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
    display: grid; /* Use grid for better layout of controls */
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); /* Responsive columns */
    gap: 20px;
    align-items: end; /* Align items to the bottom */
}

.quiz-settings-controls {
    display: flex;
    flex-direction: column;
}

.quiz-settings-controls label {
    font-weight: 600;
    margin-bottom: 8px;
    color: rgb(var(--text-color));
}

.quiz-settings-controls select {
    padding: 10px;
    border: 1px solid rgb(var(--input-border));
    border-radius: 5px;
    background-color: rgba(var(--bg-color), 0.5);
    color: rgb(var(--text-color));
    font-size: 1em;
    appearance: none; /* Remove default select arrow */
    background-image: url('data:image/svg+xml;charset=US-ASCII,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20width%3D%22292.4%22%20height%3D%22292.4%22%3E%3Cpath%20fill%3D%22%23000%22%20d%3D%22M287%2069.9a17.7%2017.7%200%200%00-13%205.2L146.2%20207.2%2018.6%2075.1c-6.8-6.8-17.7-6.8-24.5%200s-6.8%2017.7%200%2024.5l135.9%20135.9c6.8%206.8%2017.7%206.8%2024.5%200l135.9-135.9c6.8-6.8%206.8-17.7%200-24.5%200%200%200%200%200%200z%22%2F%3E%3C%2Fsvg%3E');
    background-repeat: no-repeat;
    background-position: right 10px center;
    background-size: 12px;
    cursor: pointer;
    transition: border-color 0.2s ease;
}

.quiz-settings-controls select:focus {
    outline: none;
    border-color: rgb(var(--accent-color));
}

#quiz-settings button {
    grid-column: span 1; /* Make buttons span 1 column */
    margin-top: 10px; /* Space between selects and buttons */
    /* Adjust for responsive grid alignment */
}

@media (max-width: 768px) {
    #quiz-settings {
        grid-template-columns: 1fr; /* Stack controls on small screens */
    }
    #quiz-settings button {
        grid-column: auto; /* Buttons take full width */
    }
}

.timer-display {
    font-size: 1.2em;
    font-weight: 700;
    color: rgb(var(--accent-color));
    text-align: center;
    margin-top: 20px;
    padding: 10px;
    border: 1px dashed rgb(var(--accent-color));
    border-radius: 5px;
    grid-column: 1 / -1; /* Span full width in grid */
}


.quiz-question {
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    padding: 25px;
    margin-bottom: 20px;
    box-shadow: var(--shadow);
}

.quiz-question p {
    font-size: 1.1em;
    margin-bottom: 15px;
    font-weight: 600;
}

.options-group label {
    display: block;
    margin-bottom: 10px;
    padding: 12px 15px;
    background-color: rgba(var(--bg-color), 0.5);
    border: 1px solid rgb(var(--input-border));
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s ease, border-color 0.3s ease, color 0.3s ease;
}

.options-group label:hover {
    background-color: rgba(var(--hover-color), 0.7);
    border-color: rgb(var(--accent-color));
}

.options-group input[type="radio"],
.options-group input[type="checkbox"] {
    margin-right: 10px;
    transform: scale(1.1);
}

/* Quiz Feedback Styling */
.quiz-question.correct .options-group label.selected {
    background-color: rgba(var(--correct-answer), 0.8);
    border-color: rgb(var(--correct-text));
    color: rgb(var(--correct-text));
    font-weight: 600;
}

.quiz-question.incorrect .options-group label.selected {
    background-color: rgba(var(--incorrect-answer), 0.8);
    border-color: rgb(var(--incorrect-text));
    color: rgb(var(--incorrect-text));
    font-weight: 600;
}

.quiz-question.incorrect .options-group label.correct-answer {
    background-color: rgba(var(--correct-answer), 0.8);
    border-color: rgb(var(--correct-text));
    color: rgb(var(--correct-text));
    font-weight: 600;
}

/* Hide inputs when showing feedback */
.quiz-question.correct .options-group input,
.quiz-question.incorrect .options-group input {
    pointer-events: none;
}

/* --- Buttons --- */
.btn {
    padding: 12px 25px;
    border: none;
    border-radius: 25px;
    cursor: pointer;
    font-size: 1em;
    font-weight: 600;
    transition: background-color 0.3s ease, transform 0.2s ease;
    margin-right: 10px;
    background-color: rgba(var(--button-bg-primary), 0.8);
    color: rgb(var(--button-text-primary));
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
}

.btn-primary {
    background-color: rgba(var(--button-bg-primary), 0.8);
    color: rgb(var(--button-text-primary));
}

.btn-primary:hover {
    filter: brightness(1.1);
    transform: translateY(-2px);
}

.btn-secondary {
    background-color: rgba(var(--button-bg-secondary), 0.8);
    color: rgb(var(--button-text-secondary));
}

.btn-secondary:hover {
    filter: brightness(1.1);
    transform: translateY(-2px);
}

.btn:active {
    transform: scale(0.98);
}

#quiz-controls {
    text-align: center;
    margin-top: 30px;
}

/* Quiz Results */
.quiz-results {
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    padding: 25px;
    margin-top: 30px;
    box-shadow: var(--shadow);
    text-align: center;
}

.quiz-results h3 {
    margin-top: 0;
    font-size: 1.8em;
    color: rgb(var(--accent-color));
    font-weight: 700;
}

#answer-feedback {
    margin-top: 20px;
    text-align: left;
}

.feedback-item {
    padding: 10px;
    margin-bottom: 8px;
    border-radius: 5px;
    display: flex; /* Use flexbox for button alignment */
    align-items: center; /* Vertically align items */
    justify-content: space-between; /* Space out content and button */
    flex-wrap: wrap; /* Allow wrapping on small screens */
}

.feedback-item > *:not(button) {
    flex-grow: 1; /* Allow text content to grow */
}


.feedback-item.correct {
    background-color: rgba(var(--correct-answer), 0.8);
    color: rgb(var(--correct-text));
}

.feedback-item.incorrect {
    background-color: rgba(var(--incorrect-answer), 0.8);
    color: rgb(var(--incorrect-text));
}

/* Styling for saved questions in the saved list */
.feedback-item.saved {
    background-color: rgba(var(--accent-color), 0.1); /* Light accent background */
    border-color: rgb(var(--accent-color));
    color: rgb(var(--text-color));
}

/* Small button for feedback actions */
.btn-small-feedback {
    padding: 5px 10px;
    font-size: 0.8em;
    margin-left: 10px;
    white-space: nowrap; /* Prevent button text from wrapping */
    flex-shrink: 0; /* Prevent button from shrinking */
    margin-top: 5px; /* Add a little margin for wrapping on small screens */
    margin-bottom: 5px;
}

@media (min-width: 768px) {
    .btn-small-feedback {
        margin-top: 0;
        margin-bottom: 0;
    }
}


/* Answer Filter Tabs */
.answer-filter-tabs {
    display: flex;
    justify-content: center;
    margin-top: 20px;
    margin-bottom: 20px;
    gap: 10px;
    flex-wrap: wrap;
}

.tab-button {
    padding: 8px 15px;
    border: 1px solid rgb(var(--input-border));
    border-radius: 20px;
    background-color: rgba(var(--bg-color), 0.5);
    color: rgb(var(--text-color));
    cursor: pointer;
    font-weight: 600;
    transition: background-color 0.2s ease, border-color 0.2s ease;
}

.tab-button:hover {
    background-color: rgba(var(--hover-color), 0.7);
}

.tab-button.active {
    background-color: rgb(var(--accent-color));
    color: rgb(var(--button-text-primary));
    border-color: rgb(var(--accent-color));
}

#saved-answers-container {
    text-align: left; /* Align content to the left */
    margin-top: 20px;
}

#saved-answers-list {
    margin-top: 15px;
}

/* --- Scroll to Top Button --- */
.scroll-to-top {
    position: fixed;
    bottom: 20px;
    right: 20px;
    background-color: rgba(var(--button-bg-primary), 0.8);
    color: rgb(var(--button-text-primary));
    border: 1px solid var(--glass-border);
    border-radius: 50%;
    width: 50px;
    height: 50px;
    font-size: 1.5em;
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    box-shadow: var(--shadow);
    transition: opacity 0.3s ease, transform 0.3s ease, background-color 0.3s ease;
    opacity: 0;
    pointer-events: none;
    z-index: 999;
    backdrop-filter: blur(5px);
}

.scroll-to-top.show {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(-5px);
}

.scroll-to-top:hover {
    filter: brightness(1.1);
    transform: translateY(-8px);
}

/* --- Responsive Design --- */
@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        text-align: center;
    }

    .header h1 {
        margin-bottom: 10px;
    }

    .main-nav {
        flex-direction: column;
        width: 100%;
        gap: 5px;
    }

    .nav-button {
        width: 100%;
    }

    .theme-toggle {
        justify-content: center;
        margin-top: 15px;
    }

    .section-title {
        font-size: 1.8em;
    }

    .quiz-question {
        padding: 20px;
    }

    .options-group label {
        padding: 10px;
    }

    .btn {
        width: 100%;
        margin-right: 0;
        margin-bottom: 10px;
    }

    .scroll-to-top {
        width: 45px;
        height: 45px;
        font-size: 1.3em;
        bottom: 15px;
        right: 15px;
    }

    .answer-filter-tabs .tab-button {
        flex: 1 1 auto; /* Make tabs take up available space */
    }

    .feedback-item {
        flex-direction: column; /* Stack content and button */
        align-items: flex-start; /* Align content to start */
    }

    .btn-small-feedback {
        width: auto; /* Allow button to size naturally */
        align-self: flex-end; /* Align button to the end on its own row */
    }
}