/* --- Variables for Theming --- */
:root {
    --bg-color: 248, 250, 249;
    --text-color: 40, 40, 40;
    --header-bg: 25, 135, 84;
    --header-text: 255, 255, 255;
    --card-bg: 255, 255, 255;
    --card-bg-alt: 247, 249, 252;
    --card-border: 224, 224, 224;
    --hover-color: 242, 242, 242;
    --button-bg-primary: 40, 167, 69;
    --button-text-primary: 255, 255, 255;
    --button-bg-secondary: 108, 117, 125;
    --button-text-secondary: 255, 255, 255;
    --accent-color: 25, 135, 84;
    --correct-answer: 209, 231, 221;
    --incorrect-answer: 248, 215, 218;
    --correct-text: 21, 87, 36;
    --incorrect-text: 114, 28, 36;
    --input-border: 206, 212, 218;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.05);
    --glass-border: rgba(255, 255, 255, 0.2);

    /* ELI5 Styles */
    --eli5-bg: 255, 250, 205;
    /* lemonchiffon */
    --eli5-border: 250, 218, 94;
    --eli5-text: 85, 66, 0;
}

body.dark-mode {
    --bg-color: 25, 38, 32;
    --text-color: 224, 224, 224;
    --header-bg: 20, 80, 50;
    --header-text: 255, 255, 255;
    --card-bg: 30, 50, 40;
    --card-bg-alt: 35, 55, 45;
    --card-border: 70, 90, 80;
    --hover-color: 35, 60, 48;
    --button-bg-primary: 60, 190, 113;
    --button-text-primary: 25, 38, 32;
    --button-bg-secondary: 90, 100, 110;
    --button-text-secondary: 255, 255, 255;
    --accent-color: 75, 192, 120;
    --correct-answer: 30, 80, 55;
    --incorrect-answer: 80, 40, 45;
    --correct-text: 120, 220, 160;
    --incorrect-text: 230, 130, 140;
    --input-border: 102, 102, 102;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
    --glass-border: rgba(0, 0, 0, 0.2);

    /* ELI5 Dark Styles */
    --eli5-bg: 47, 51, 58;
    --eli5-border: 91, 99, 112;
    --eli5-text: 220, 221, 222;
}

/* --- Base Styles --- */
body {
    font-family: 'Inter', sans-serif;
    margin: 0;
    padding: 0;
    background: rgb(var(--bg-color));
    color: rgb(var(--text-color));
    transition: background 0.3s ease, color 0.3s ease;
    line-height: 1.6;
}

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

/* --- Header & Navigation (Modernized) --- */
.header {
    background-color: rgba(var(--header-bg), 0.8);
    backdrop-filter: blur(10px);
    color: rgb(var(--header-text));
    padding: 10px 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: 0 20px;
}

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

.header-right {
    display: flex;
    align-items: center;
    gap: 20px;
}

.main-nav {
    display: flex;
    gap: 5px;
    /* Reduced gap for closer buttons */
    position: relative;
}

.nav-button {
    background-color: transparent;
    border: none;
    color: rgba(var(--header-text), 0.85);
    padding: 12px 20px;
    /* Increased padding */
    border-radius: 8px;
    /* Softer radius */
    cursor: pointer;
    font-size: 1em;
    /* Increased font size */
    font-weight: 600;
    transition: all 0.3s ease;
    position: relative;
}

.nav-button:hover {
    background-color: rgba(255, 255, 255, 0.1);
    color: rgb(var(--header-text));
    transform: translateY(-2px);
    /* Keep hover animation */
}

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

/* Floating Highlight */
.nav-button.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 15%;
    right: 15%;
    height: 3px;
    background: rgb(var(--header-text));
    border-radius: 2px;
}


/* --- Theme Toggle --- */
.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 {
    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: 2.2em;
    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 (Collapsible Cards - Improved Readability) --- */
.collapsible-card {
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 12px;
    /* Softer radius */
    margin-bottom: 25px;
    /* Increased spacing */
    box-shadow: var(--shadow);
    overflow: hidden;
    transition: background-color 0.3s ease;
}

/* Alternating background for topics */
#notes-section .collapsible-card:nth-child(even) {
    background-color: rgba(var(--card-bg-alt), 0.9);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 25px;
    /* Increased padding */
    cursor: pointer;
    border-bottom: 1px solid rgb(var(--card-border));
    transition: background-color 0.2s ease;
}

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

.header-main-content {
    display: flex;
    align-items: center;
    gap: 20px;
    flex-grow: 1;
}

.topic-title {
    margin: 0;
    font-size: 1.4em;
    /* Larger title */
    font-weight: 600;
}

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

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

.card-content {
    padding: 0 25px;
    /* Increased padding */
    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: 10000px;
    /* Increased max-height */
    padding-top: 25px;
    padding-bottom: 25px;
    opacity: 1;
    overflow-y: auto;
}

.card-content h4 {
    color: rgb(var(--accent-color));
    margin-top: 25px;
    margin-bottom: 10px;
    border-bottom: 1px dashed rgb(var(--card-border));
    padding-bottom: 8px;
}

.card-content ul,
.card-content ol {
    padding-left: 25px;
    margin-bottom: 15px;
}

.card-content li {
    margin-bottom: 10px;
}


/* --- ELI5 Button and Explanation Styling --- */
.eli5-button {
    background-color: rgba(var(--accent-color), 0.1);
    color: rgb(var(--accent-color));
    border: 1px solid rgba(var(--accent-color), 0.5);
    border-radius: 20px;
    padding: 6px 12px;
    font-size: 0.8em;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    gap: 6px;
}

.eli5-button:hover {
    background-color: rgba(var(--accent-color), 0.2);
    transform: scale(1.05);
}

.eli5-explanation {
    font-family: 'Comic Sans MS', 'Chalkboard SE', 'Comic Neue', sans-serif;
    background-color: rgb(var(--eli5-bg));
    color: rgb(var(--eli5-text));
    border: 2px dashed rgb(var(--eli5-border));
    border-radius: 10px;
    padding: 20px;
    margin-top: 25px;
    line-height: 1.8;
    font-size: 1.1em;
    opacity: 0;
    max-height: 0;
    overflow: hidden;
    transition: opacity 0.4s ease-out, max-height 0.4s ease-out, margin-top 0.4s ease-out, padding 0.4s ease-out;
}

.eli5-explanation.visible {
    opacity: 1;
    max-height: 2000px;
    padding: 20px;
}

/* --- Form and Modal Styles --- */
.form-container {
    max-width: 700px;
    margin: 20px auto;
    padding: 30px;
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 600;
}

.form-group input[type="text"],
.form-group input[type="email"],
.form-group input[type="password"],
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 12px;
    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;
    box-sizing: border-box;
}

.form-container hr {
    border: 0;
    height: 1px;
    background: rgb(var(--card-border));
    margin: 25px 0;
}

.option-item {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 10px;
}

.option-item input[type="text"] {
    flex-grow: 1;
}

.option-item .remove-option-btn {
    background: none;
    border: none;
    color: rgb(var(--incorrect-text));
    font-size: 1.2em;
    cursor: pointer;
}

.error-message,
.success-message {
    padding: 10px;
    border-radius: 5px;
    margin-bottom: 15px;
    text-align: center;
    display: none;
}

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

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

.modal {
    display: none;
    position: fixed;
    z-index: 1001;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, 0.6);
    backdrop-filter: blur(5px);
}

.modal-content {
    background-color: rgb(var(--card-bg));
    margin: 15% auto;
    padding: 30px;
    border: 1px solid rgb(var(--card-border));
    border-radius: 8px;
    width: 90%;
    max-width: 500px;
    position: relative;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

.modal-content .close-btn {
    color: #aaa;
    float: right;
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    line-height: 1;
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-top: 20px;
}

/* --- Quiz Section Styling --- */
#quiz-settings {
    background-color: rgba(var(--card-bg), 0.9);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    padding: 25px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    align-items: end;
}

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

.quiz-settings-controls label {
    font-weight: 600;
    margin-bottom: 8px;
}

.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;
    cursor: pointer;
}

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

.quiz-question {
    background-color: rgba(var(--card-bg), 0.9);
    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;
}

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

.options-group input {
    margin-right: 10px;
}

/* --- Quiz Feedback Styling --- */
.quiz-question.correct .options-group label.selected,
.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;
}

.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.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;
}

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

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

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

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

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

.btn-report {
    background-color: rgba(255, 193, 7, 0.2);
    color: #b98900;
    border: 1px solid #b98900;
    padding: 5px 10px;
    font-size: 0.8em;
    margin-left: 10px;
    border-radius: 5px;
    white-space: nowrap;
    flex-shrink: 0;
}

body.dark-mode .btn-report {
    color: #ffc107;
    border-color: #ffc107;
}

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

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

.quiz-results h3 {
    font-size: 1.8em;
    color: rgb(var(--accent-color));
}

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

.feedback-item {
    padding: 15px;
    margin-bottom: 10px;
    border-radius: 5px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 10px;
}

.feedback-item>div {
    flex-grow: 1;
}

.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));
}

.answer-filter-tabs {
    display: flex;
    justify-content: center;
    margin: 20px 0;
    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.active,
.tab-button:hover {
    background-color: rgb(var(--accent-color));
    color: rgb(var(--button-text-primary));
    border-color: rgb(var(--accent-color));
}

#saved-answers-container {
    text-align: left;
    margin-top: 20px;
}

/* --- 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: none;
    justify-content: center;
    align-items: center;
    cursor: pointer;
    box-shadow: var(--shadow);
    z-index: 999;
    backdrop-filter: blur(5px);
}

.scroll-to-top.show {
    display: flex;
}


/* --- Structured Practice Section --- */
.structured-question-card {
    background-color: rgba(var(--card-bg), 0.9);
    backdrop-filter: blur(5px);
    border: 1px solid var(--glass-border);
    border-radius: 8px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
    padding: 25px;
}

.structured-question-card h3 {
    color: rgb(var(--accent-color));
    margin-top: 0;
}

.user-answer-area {
    width: 100%;
    padding: 12px;
    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;
    box-sizing: border-box;
    margin: 15px 0;
    font-family: inherit;
    line-height: 1.6;
}

.grading-results {
    margin-top: 25px;
    padding: 20px;
    border-top: 2px solid rgb(var(--card-border));
    background-color: rgba(var(--hover-color), 0.5);
    border-radius: 0 0 8px 8px;
}

.grading-results h4 {
    margin-top: 0;
    color: rgb(var(--accent-color));
}

.ideal-answer-box {
    background-color: rgba(var(--bg-color), 0.7);
    padding: 15px;
    border: 1px dashed rgb(var(--input-border));
    border-radius: 5px;
    line-height: 1.7;
    white-space: pre-wrap;
}

/* --- Responsive Design --- */
@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        text-align: center;
        gap: 15px;
        padding-bottom: 15px;
    }

    .header-right {
        flex-direction: column;
        width: 100%;
    }

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

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

    #quiz-settings {
        grid-template-columns: 1fr;
    }

    .feedback-item {
        flex-direction: column;
        align-items: flex-start;
    }
}

/* Footer Styles */
.site-footer {
    background-color: rgba(var(--header-bg), 0.8);
    color: rgb(var(--header-text));
    padding: 20px 0;
    text-align: center;
    border-top: 1px solid var(--glass-border);
    margin-top: 40px;
    flex-shrink: 0;
}

.site-footer p {
    margin: 5px 0;
    font-size: 0.9em;
}

/* makes any image scale down within its container */
img {
    max-width: 100%;
    height: auto;
    padding-bottom: 10px;
}