/* Custom Global Resets & Theme Colors (Light Mode) */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

body {
    background-color: #f8fafc; /* Crisp, clean soft-light background */
    color: #1e293b; /* Premium slate dark text */
    min-height: 100vh;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 3rem 2rem;
}

/* Nav Bar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.85rem 2.5rem;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid #e2e8f0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.03);
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.nav-right {
    display: flex;
    align-items: center;
    gap: 0.6rem;
}

.nav-action-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0.45rem 0.85rem;
    border-radius: 8px;
    border: 1px solid #e2e8f0;
    background-color: #ffffff;
    color: #334155;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.nav-action-btn:hover {
    background-color: #f1f5f9;
    border-color: #cbd5e1;
    color: #0f172a;
}

.shortcut-pill {
    font-family: inherit;
    font-size: 0.7rem;
    background-color: #f1f5f9;
    color: #64748b;
    padding: 0.15rem 0.35rem;
    border-radius: 4px;
    border: 1px solid #e2e8f0;
}

.logo {
    font-size: 1.45rem;
    font-weight: 700;
    color: #0f172a;
    cursor: pointer;
    letter-spacing: -0.02em;
    text-decoration: none;
    display: inline-block;
}

.logo span {
    color: #2563eb;
}

.badge {
    background-color: #eff6ff;
    border: 1px solid #bfdbfe;
    color: #2563eb;
    padding: 0.25rem 0.7rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 600;
}

/* Tabs Navigation Bar */
.tabs-nav-bar {
    background-color: #ffffff;
    border-bottom: 1px solid #e2e8f0;
    position: sticky;
    top: 55px;
    z-index: 90;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.02);
}

.tabs-scroll-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0.6rem 2rem;
    display: flex;
    gap: 0.6rem;
    overflow-x: auto;
    scrollbar-width: none;
    -webkit-overflow-scrolling: touch;
}

.tabs-scroll-container::-webkit-scrollbar {
    display: none;
}

.nav-tab {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0.5rem 1rem;
    border-radius: 9999px;
    border: 1px solid #e2e8f0;
    background-color: #f8fafc;
    color: #475569;
    font-size: 0.88rem;
    font-weight: 600;
    cursor: pointer;
    white-space: nowrap;
    transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
    flex-shrink: 0;
    text-decoration: none;
}

.nav-tab:hover {
    background-color: #f1f5f9;
    color: #0f172a;
    border-color: #cbd5e1;
}

.nav-tab.active {
    background-color: #2563eb;
    color: #ffffff;
    border-color: #2563eb;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.25);
}

.tab-icon {
    font-size: 1rem;
}

/* Hero Content headers */
.hero-section {
    margin-bottom: 2.5rem;
    max-width: 820px;
}

.hero-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background-color: #eff6ff;
    border: 1px solid #bfdbfe;
    color: #1d4ed8;
    padding: 0.35rem 0.9rem;
    border-radius: 9999px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
    letter-spacing: 0.2px;
}

.pill-dot {
    width: 8px;
    height: 8px;
    background-color: #2563eb;
    border-radius: 50%;
    box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.2);
}

.hero-title {
    font-size: clamp(2rem, 4vw, 2.75rem);
    font-weight: 800;
    color: #0f172a;
    line-height: 1.2;
    margin-bottom: 0.85rem;
    letter-spacing: -0.02em;
}

.gradient-text {
    background: linear-gradient(135deg, #2563eb 0%, #7c3aed 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-subtitle {
    color: #475569;
    font-size: 1.05rem;
    line-height: 1.6;
    margin-bottom: 1.25rem;
}

/* Search Bar Styling */
.search-box-container {
    position: relative;
    margin: 1.5rem 0 1.75rem 0;
    max-width: 720px;
}

.search-input-wrapper {
    display: flex;
    align-items: center;
    position: relative;
    background-color: #ffffff;
    border: 2px solid #e2e8f0;
    border-radius: 12px;
    padding: 0.35rem 0.85rem;
    box-shadow: 0 4px 12px -2px rgba(0, 0, 0, 0.05);
    transition: all 0.25s ease;
}

.search-input-wrapper:focus-within {
    border-color: #2563eb;
    box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.12), 0 4px 16px rgba(0, 0, 0, 0.06);
}

.search-input-icon {
    font-size: 1.15rem;
    margin-right: 0.6rem;
    color: #64748b;
}

#global-search-input {
    width: 100%;
    border: none;
    outline: none;
    font-size: 1rem;
    color: #0f172a;
    background: transparent;
    padding: 0.6rem 0;
    font-family: inherit;
}

#global-search-input::placeholder {
    color: #94a3b8;
}

.search-clear-btn {
    background: #e2e8f0;
    border: none;
    color: #475569;
    font-size: 0.85rem;
    border-radius: 50%;
    width: 22px;
    height: 22px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    margin: 0 0.5rem;
    transition: background 0.2s;
}

.search-clear-btn:hover {
    background: #cbd5e1;
    color: #0f172a;
}

.search-shortcut-hint {
    display: flex;
    align-items: center;
    gap: 0.2rem;
}

.search-shortcut-hint kbd {
    font-family: inherit;
    font-size: 0.72rem;
    font-weight: 600;
    color: #64748b;
    background: #f1f5f9;
    border: 1px solid #cbd5e1;
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
}

/* Search Results Container */
.search-results-container {
    position: absolute;
    top: calc(100% + 8px);
    left: 0;
    right: 0;
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    box-shadow: 0 12px 32px -4px rgba(0, 0, 0, 0.12);
    max-height: 480px;
    overflow-y: auto;
    z-index: 100;
    padding: 1rem;
    animation: fadeIn 0.2s ease-in-out;
}

.search-results-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-bottom: 0.75rem;
    margin-bottom: 0.75rem;
    border-bottom: 1px solid #f1f5f9;
}

.search-results-count {
    font-size: 0.85rem;
    font-weight: 700;
    color: #475569;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.btn-close-results {
    background: transparent;
    border: none;
    color: #64748b;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
}

.btn-close-results:hover {
    color: #0f172a;
    background: #f1f5f9;
}

.search-results-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.search-result-card {
    padding: 0.9rem 1rem;
    background-color: #f8fafc;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s ease;
    text-align: left;
    text-decoration: none;
    color: inherit;
    display: block;
}

.search-result-card:hover {
    background-color: #ffffff;
    border-color: #2563eb;
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(37, 99, 235, 0.08);
}

.search-result-meta {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.4rem;
    flex-wrap: wrap;
}

.badge-sub {
    font-size: 0.72rem;
    font-weight: 700;
    padding: 0.15rem 0.5rem;
    border-radius: 4px;
    text-transform: uppercase;
}

.badge-science { background: #ecfdf5; color: #059669; }
.badge-sst { background: #fffbeb; color: #d97706; }
.badge-maths { background: #eff6ff; color: #2563eb; }
.badge-english { background: #f5f3ff; color: #7c3aed; }
.badge-hindi { background: #fff1f2; color: #e11d48; }

.badge-branch {
    font-size: 0.72rem;
    font-weight: 600;
    background: #e2e8f0;
    color: #475569;
    padding: 0.15rem 0.45rem;
    border-radius: 4px;
}

.search-result-chap {
    font-size: 0.78rem;
    color: #64748b;
    font-weight: 500;
}

.search-result-q {
    font-size: 0.92rem;
    font-weight: 600;
    color: #0f172a;
    margin-bottom: 0.25rem;
    line-height: 1.4;
}

.search-result-a {
    font-size: 0.85rem;
    color: #64748b;
    line-height: 1.4;
}

.search-highlight {
    background-color: #fef08a;
    color: #854d0e;
    padding: 0.1rem 0.2rem;
    border-radius: 3px;
    font-weight: 700;
}

.search-empty-state {
    padding: 1.5rem;
    text-align: center;
    color: #64748b;
    font-size: 0.95rem;
    line-height: 1.5;
}

.features-pills {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
    margin-top: 1rem;
}

.feat-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    background: #ffffff;
    border: 1px solid #e2e8f0;
    padding: 0.4rem 0.85rem;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 500;
    color: #334155;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.03);
}

.feat-icon {
    font-size: 0.95rem;
}

.view-layer {
    opacity: 1;
    animation: fadeIn 0.25s ease-out forwards;
}

.hidden {
    display: none !important;
}

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

/* Breadcrumb Navigation Buttons */
.navigation-crumbs {
    margin-bottom: 1.5rem;
}

.btn-back {
    display: inline-flex;
    align-items: center;
    background-color: #ffffff;
    color: #64748b;
    border: 1px solid #cbd5e1;
    padding: 0.6rem 1.2rem;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 500;
    transition: all 0.2s;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
    text-decoration: none;
}

.btn-back:hover {
    color: #ffffff;
    background-color: #2563eb;
    border-color: #2563eb;
}

/* LAYER 1: Big Grid Subject Buttons */
.subject-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(270px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2.5rem;
}

.subject-card-btn {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    padding: 1.75rem;
    border-radius: 14px;
    cursor: pointer;
    text-align: left;
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    background-color: #ffffff;
    border: 1px solid #e2e8f0;
    box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.04), 0 2px 4px -2px rgba(0, 0, 0, 0.03);
    position: relative;
    overflow: hidden;
    text-decoration: none;
    color: inherit;
}

.subject-card-btn:hover {
    transform: translateY(-5px);
    box-shadow: 0 14px 28px -4px rgba(0, 0, 0, 0.08), 0 6px 12px -3px rgba(0, 0, 0, 0.05);
}

.subject-card-btn:focus-visible {
    outline: 2px solid #2563eb;
    outline-offset: 2px;
}

/* Card Header */
.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.2rem;
}

.card-icon-wrapper {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    transition: transform 0.25s ease;
}

.subject-card-btn:hover .card-icon-wrapper {
    transform: scale(1.08);
}

.card-tag {
    font-size: 0.75rem;
    font-weight: 700;
    padding: 0.3rem 0.65rem;
    border-radius: 6px;
    letter-spacing: 0.3px;
    text-transform: uppercase;
}

/* Card Body */
.card-body {
    flex-grow: 1;
    margin-bottom: 1.25rem;
}

.card-title {
    font-size: 1.35rem;
    font-weight: 700;
    color: #0f172a;
    margin-bottom: 0.45rem;
    letter-spacing: -0.01em;
}

.card-desc {
    font-size: 0.92rem;
    color: #64748b;
    line-height: 1.55;
}

/* Card Footer */
.card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 1rem;
    border-top: 1px solid #f1f5f9;
    font-size: 0.9rem;
    font-weight: 600;
    transition: color 0.2s;
}

.card-arrow {
    font-size: 1.1rem;
    transition: transform 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.subject-card-btn:hover .card-arrow {
    transform: translateX(5px);
}

/* Specific Subject Themes */
/* 1. Science (Emerald) */
.card-science {
    border-top: 4px solid #10b981;
}
.card-science:hover {
    border-color: #10b981;
}
.icon-science {
    background-color: #ecfdf5;
    border: 1px solid #a7f3d0;
}
.card-science .card-tag {
    background-color: #ecfdf5;
    color: #059669;
}
.card-science .card-footer {
    color: #059669;
}

/* 2. SST (Amber / Orange) */
.card-sst {
    border-top: 4px solid #f59e0b;
}
.card-sst:hover {
    border-color: #f59e0b;
}
.icon-sst {
    background-color: #fffbeb;
    border: 1px solid #fde68a;
}
.card-sst .card-tag {
    background-color: #fffbeb;
    color: #d97706;
}
.card-sst .card-footer {
    color: #d97706;
}

/* 3. Maths (Royal Blue) */
.card-maths {
    border-top: 4px solid #3b82f6;
}
.card-maths:hover {
    border-color: #3b82f6;
}
.icon-maths {
    background-color: #eff6ff;
    border: 1px solid #bfdbfe;
}
.card-maths .card-tag {
    background-color: #eff6ff;
    color: #2563eb;
}
.card-maths .card-footer {
    color: #2563eb;
}

/* 4. English (Violet) */
.card-english {
    border-top: 4px solid #8b5cf6;
}
.card-english:hover {
    border-color: #8b5cf6;
}
.icon-english {
    background-color: #f5f3ff;
    border: 1px solid #ddd6fe;
}
.card-english .card-tag {
    background-color: #f5f3ff;
    color: #7c3aed;
}
.card-english .card-footer {
    color: #7c3aed;
}

/* 5. Hindi (Rose / Crimson) */
.card-hindi {
    border-top: 4px solid #e11d48;
}
.card-hindi:hover {
    border-color: #e11d48;
}
.icon-hindi {
    background-color: #fff1f2;
    border: 1px solid #fecdd3;
}
.card-hindi .card-tag {
    background-color: #fff1f2;
    color: #e11d48;
}
.card-hindi .card-footer {
    color: #e11d48;
}

/* Student Creator Note Callout */
.creator-banner {
    display: flex;
    align-items: flex-start;
    gap: 1.25rem;
    background: linear-gradient(135deg, #ffffff, #f8fafc);
    border: 1px solid #e2e8f0;
    border-left: 4px solid #2563eb;
    border-radius: 12px;
    padding: 1.5rem;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.02);
}

.creator-avatar {
    width: 44px;
    height: 44px;
    background-color: #eff6ff;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.4rem;
    flex-shrink: 0;
}

.creator-content h4 {
    font-size: 1.05rem;
    font-weight: 700;
    color: #0f172a;
    margin-bottom: 0.35rem;
}

.creator-content p {
    font-size: 0.92rem;
    color: #475569;
    line-height: 1.6;
    margin: 0;
}

/* LAYER 2: Chapter Buttons Layout */
.chapters-buttons-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1rem;
}

.chapter-select-btn {
    background-color: #ffffff;
    border: 1px solid #e2e8f0;
    color: #1e293b;
    padding: 1.25rem 1.5rem;
    border-radius: 12px;
    text-align: left;
    font-size: 1.05rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.02);
    text-decoration: none;
}

.chapter-select-btn:hover {
    background-color: #f8fafc;
    border-color: #2563eb;
    transform: translateX(4px);
    box-shadow: 0 6px 16px -2px rgba(37, 99, 235, 0.1), 0 2px 6px -1px rgba(0, 0, 0, 0.04);
}

.chapter-select-btn::after {
    content: "View Solutions →";
    font-size: 0.85rem;
    color: #2563eb;
    font-weight: 700;
    flex-shrink: 0;
    margin-left: 0.75rem;
    transition: transform 0.2s ease;
}

.chapter-select-btn:hover::after {
    transform: translateX(3px);
}

.branch-select-btn::after {
    content: "Explore Chapters →";
    color: #2563eb;
}

.chap-btn-content {
    display: flex;
    align-items: center;
    gap: 1.15rem;
    flex: 1;
    min-width: 0;
}

.chap-icon-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 46px;
    height: 46px;
    font-size: 1.45rem;
    background: #f8fafc;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    flex-shrink: 0;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

.chapter-select-btn:hover .chap-icon-badge {
    transform: scale(1.12);
    background: #eff6ff;
    border-color: #93c5fd;
    box-shadow: 0 4px 10px rgba(37, 99, 235, 0.12);
}

.branch-icon-badge {
    background: #eff6ff;
    border-color: #bfdbfe;
}

.branch-text-wrapper {
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}

.branch-chap-count {
    font-size: 0.82rem;
    font-weight: 500;
    color: #64748b;
}

.chap-btn-title {
    font-size: 1.05rem;
    font-weight: 600;
    color: #1e293b;
    line-height: 1.45;
    word-break: break-word;
}

.heading-icon-badge {
    display: inline-block;
    margin-right: 0.45rem;
    font-size: 1.1em;
    vertical-align: -0.06em;
}

/* LAYER 3: Final Q&A Boxes Stack */
.solutions-stack {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}
.ncert-table {
    width: 100%;
    max-width: 850px;
    margin: 1.5rem auto;
    border-collapse: collapse;
    background: #ffffff;
    font-size: 1rem;
}

.ncert-table th,
.ncert-table td {
    border: 1px solid #e2e8f0;
    padding: 0.8rem 1rem;
    text-align: left;
}

.ncert-table th {
    font-weight: 700;
    background-color: #f8fafc;
}

.ncert-table td:first-child,
.ncert-table th:first-child {
    text-align: center;
    width: 90px;
}

@media (max-width: 600px) {
    .ncert-table {
        font-size: 0.85rem;
    }

    .ncert-table th,
    .ncert-table td {
        padding: 0.6rem;
    }
}
/* ============================================================ */
/* GENERALIZED QUESTION & ANSWER CARD STYLING                  */
/* ============================================================ */
.solution-card {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    width: 100%;
    max-width: 100%;
    box-sizing: border-box;
    background-color: #ffffff;
    border: 1px solid #e2e8f0;
    padding: 1.6rem 1.8rem;
    border-radius: 12px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.03);
    transition: all 0.25s ease;
    position: relative;
}

.solution-card:hover {
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.05);
    border-color: #cbd5e1;
}

/* Question Header & Badge */
.card-question-header {
    display: flex;
    align-items: flex-start;
    gap: 0.85rem;
    margin-bottom: 0.75rem;
    width: 100%;
}

.q-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: #eff6ff;
    border: 1px solid #bfdbfe;
    color: #2563eb;
    font-size: 0.82rem;
    font-weight: 800;
    padding: 0.35rem 0.65rem;
    border-radius: 6px;
    flex-shrink: 0;
    margin-top: 5px;
    letter-spacing: 0.3px;
}

/* Generalized Question Box (replaces inline styles from script.js) */
.question-text {
    flex-grow: 1;
    display: block;
    width: 100%;
    box-sizing: border-box;
    background-color: #fbfbfb;
    border: 1px solid #e0e0e0;
    border-radius: 6px;
    padding: 12px 16px;
    font-size: 1.05rem;
    font-weight: 700;
    color: #333333;
    line-height: 1.55;
    white-space: normal;
    word-break: break-word;
    overflow-wrap: break-word;
}

.question-text p {
    margin: 0 0 8px 0;
    color: inherit;
    font-weight: inherit;
    line-height: inherit;
    font-size: inherit;
}

.question-text p:last-child {
    margin-bottom: 0;
}

.question-text h2,
.answer-text h2 {
    margin: 0 0 8px 0;
    color: #cfa670;
    font-size: 16px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.question-text table,
.answer-text table {
    width: 100%;
    border-collapse: collapse;
    font-size: 13.5px;
    margin: 10px 0;
}

.question-text th,
.answer-text th {
    background: #eedcb6;
    padding: 6px 10px;
    border: 1px solid #d4c2a8;
    text-align: left;
    font-weight: 700;
    color: #333333;
}

.question-text td,
.answer-text td {
    padding: 6px 10px;
    border: 1px solid #d4c2a8;
    color: #333333;
}

.question-text ol,
.question-text ul {
    margin: 8px 0;
    padding-left: 20px;
    line-height: 1.6;
    color: #333333;
}

.question-text li {
    margin-bottom: 6px;
    line-height: 1.6;
}

.question-text li:last-child {
    margin-bottom: 0;
}

/* Prevents duplicated inner boxes if previously wrapped in an inline style div */
.question-text > div {
    background: transparent !important;
    border: none !important;
    padding: 0 !important;
    margin: 0 !important;
    border-radius: 0 !important;
}

/* Question Diagram Image */
.question-image {
    max-width: 420px;
    width: 100%;
    height: auto;
    display: block;
    margin: 1.25rem auto;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
    border: 1px solid #e2e8f0;
}

/* Generalized Answer Box (warm gold accent & soft cream background from script.js) */
.answer-text {
    display: block;
    width: 100%;
    box-sizing: border-box;
    background-color: #fdfaf2;
    border-left: 4px solid #cfa670;
    border-radius: 4px;
    padding: 16px 20px;
    margin-top: 0.75rem;
    margin-bottom: 0.5rem;
    color: #444444;
    font-size: 0.98rem;
    line-height: 1.65;
    word-break: break-word;
    overflow-wrap: break-word;
    white-space: pre-line;
}

/* Child lists, paragraphs, and formatting inside Answers */
.answer-text ul,
.answer-text ol,
.answer-text p,
.answer-text table,
.answer-text div {
    white-space: normal;
}

.answer-text ul,
.answer-text ol {
    margin: 0.4rem 0;
    padding-left: 20px;
    line-height: 1.65;
    color: #444444;
}

.answer-text li {
    margin-bottom: 6px;
    line-height: 1.65;
}

.answer-text li:last-child {
    margin-bottom: 0;
}

.answer-text p {
    margin: 0 0 0.75rem 0;
    line-height: 1.65;
    color: #444444;
}

.answer-text p:last-child {
    margin-bottom: 0;
}

.answer-text strong,
.answer-text b {
    font-weight: 700;
    color: #1e293b;
}

.answer-text img {
    max-width: 100%;
    height: auto;
    border-radius: 6px;
    display: block;
}

/* Prevents duplicate nesting from legacy inline wrappers */
.answer-text > div:not([style*="display: flex"]):not([style*="text-align: center"]):not([style*="max-width"]) {
    background: transparent !important;
    border: none !important;
    padding: 0 !important;
    margin: 0 !important;
    border-radius: 0 !important;
}

.card-actions-bar {
    margin-top: 1.25rem;
    display: flex;
    justify-content: flex-end;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
    width: 100%;
}

.btn-copy-solution {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    background-color: #ffffff;
    color: #475569;
    border: 1px solid #cbd5e1;
    padding: 0.45rem 0.95rem;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    text-decoration: none;
}

.btn-copy-solution:hover {
    background-color: #f8fafc;
    border-color: #2563eb;
    color: #2563eb;
}

.btn-copy-solution.btn-copied {
    background-color: #10b981 !important;
    border-color: #10b981 !important;
    color: #ffffff !important;
}

.highlight-target {
    animation: highlightPulse 2.5s ease-out;
    border-color: #2563eb !important;
    box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.25) !important;
}

@keyframes highlightPulse {
    0% { background-color: #eff6ff; }
    50% { background-color: #eff6ff; }
    100% { background-color: #ffffff; }
}

/* ============================================================ */
/* EXERCISE SET SELECTOR & INTERACTIVE HINT / SOLUTION TOGGLES  */
/* ============================================================ */
.exercise-select-btn::after {
    content: "View Solutions →";
    color: #2563eb;
}

.exercise-all-btn {
    background: linear-gradient(135deg, #eff6ff 0%, #f8fafc 100%);
    border: 1.5px solid #93c5fd;
}

.exercise-all-btn::after {
    content: "View All Sets →";
    color: #1d4ed8;
}

.exercise-switcher-bar {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.55rem;
    margin-bottom: 1.5rem;
    padding: 0.85rem 1rem;
    background: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.03);
}

.exercise-switcher-label {
    font-size: 0.82rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: #64748b;
    margin-right: 0.35rem;
}

.exercise-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    padding: 0.45rem 0.9rem;
    border-radius: 9999px;
    font-size: 0.86rem;
    font-weight: 600;
    color: #334155;
    background: #f8fafc;
    border: 1px solid #cbd5e1;
    text-decoration: none;
    transition: all 0.2s ease;
    cursor: pointer;
}

.exercise-pill:hover {
    background: #eff6ff;
    border-color: #60a5fa;
    color: #1d4ed8;
}

.exercise-pill.active {
    background: #2563eb;
    border-color: #2563eb;
    color: #ffffff;
    box-shadow: 0 2px 8px rgba(37, 99, 235, 0.25);
}

.exercise-pill-count {
    font-size: 0.74rem;
    padding: 0.1rem 0.42rem;
    border-radius: 999px;
    background: rgba(15, 23, 42, 0.08);
    color: inherit;
}

.exercise-pill.active .exercise-pill-count {
    background: rgba(255, 255, 255, 0.22);
    color: #ffffff;
}

/* Interactive Hint / Critical Formula Box */
.hint-box {
    width: 100%;
    box-sizing: border-box;
    background-color: #fffbeb;
    border: 1px solid #fde68a;
    border-left: 4px solid #f59e0b;
    border-radius: 6px;
    padding: 12px 16px;
    margin-top: 0.5rem;
    margin-bottom: 0.25rem;
    color: #78350f;
    font-size: 0.94rem;
    line-height: 1.6;
    transition: all 0.2s ease;
}

.hint-box.hidden {
    display: none;
}

.hint-box-header {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-weight: 700;
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.4px;
    color: #b45309;
    margin-bottom: 4px;
}

.btn-toggle-hint {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    background-color: #fffbeb;
    color: #b45309;
    border: 1px solid #fcd34d;
    padding: 0.45rem 0.95rem;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-toggle-hint:hover,
.btn-toggle-hint.active {
    background-color: #fef3c7;
    border-color: #f59e0b;
    color: #92400e;
}

.btn-toggle-solution {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    background-color: #f8fafc;
    color: #334155;
    border: 1px solid #cbd5e1;
    padding: 0.45rem 0.95rem;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-toggle-solution:hover {
    background-color: #eff6ff;
    border-color: #2563eb;
    color: #2563eb;
}

.answer-text.hidden {
    display: none;
}

/* Floating Controls */
.floating-controls {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
    z-index: 900;
}

.floating-btn {
    display: flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0.65rem 1.1rem;
    border-radius: 9999px;
    border: 1px solid #e2e8f0;
    background-color: #ffffff;
    color: #0f172a;
    font-size: 0.88rem;
    font-weight: 700;
    cursor: pointer;
    box-shadow: 0 6px 16px -2px rgba(0, 0, 0, 0.1);
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

.back-to-top-btn {
    width: 44px;
    height: 44px;
    padding: 0;
    justify-content: center;
    border-radius: 50%;
    font-size: 1.2rem;
    align-self: flex-end;
}

.back-to-top-btn:hover {
    transform: translateY(-3px);
    background-color: #f8fafc;
    border-color: #2563eb;
    color: #2563eb;
}

/* Toast System */
.toast-container {
    position: fixed;
    bottom: 1.5rem;
    left: 50%;
    transform: translateX(-50%);
    z-index: 1200;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    pointer-events: none;
}

.toast-item {
    background-color: #0f172a;
    color: #ffffff;
    padding: 0.7rem 1.25rem;
    border-radius: 9999px;
    font-size: 0.88rem;
    font-weight: 600;
    box-shadow: 0 10px 25px -3px rgba(0, 0, 0, 0.2);
    opacity: 0;
    transform: translateY(10px);
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.toast-item.show {
    opacity: 1;
    transform: translateY(0);
}

.toast-success {
    background-color: #059669;
}

.toast-error {
    background-color: #dc2626;
}

/* Responsive UI: Mobile & PC */
@media (max-width: 768px) {
    .navbar {
        padding: 0.75rem 1.25rem;
    }
    .nav-action-btn .btn-text,
    .shortcut-pill {
        display: none;
    }
    .tabs-nav-bar {
        top: 50px;
    }
    .tabs-scroll-container {
        padding: 0.5rem 1rem;
    }
    .container {
        padding: 1.5rem 1rem;
    }
    .hero-title {
        font-size: 1.85rem;
    }
    .hero-subtitle {
        font-size: 0.95rem;
    }
    .search-box-container {
        margin: 1.25rem 0;
    }
    .subject-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    .creator-banner {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.75rem;
        padding: 1.25rem;
    }
    .floating-controls {
        bottom: 1rem;
        right: 1rem;
    }
    .floating-btn-text {
        display: none;
    }
    .chapter-select-btn {
        padding: 1rem 1.1rem;
        gap: 0.75rem;
    }
    .chap-btn-content {
        gap: 0.75rem;
    }
    .chap-icon-badge {
        width: 38px;
        height: 38px;
        font-size: 1.25rem;
        border-radius: 9px;
    }
    .chap-btn-title {
        font-size: 0.95rem;
    }
    .chapter-select-btn::after {
        font-size: 0.75rem;
    }
}





/* ============================================================ */
/* DISABLED / INTRODUCTORY CHAPTER CARDS (NO EXERCISES)        */
/* ============================================================ */
.chapter-select-btn.chapter-no-exercises {
    background: #f8fafc;
    border: 1.5px dashed #cbd5e1;
    cursor: not-allowed;
    position: relative;
    user-select: none;
    box-shadow: none;
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

.chapter-select-btn.chapter-no-exercises::after {
    display: none !important;
}

.chapter-select-btn.chapter-no-exercises .chap-icon-badge {
    background: #f1f5f9;
    border-color: #e2e8f0;
    filter: grayscale(0.4);
    transition: all 0.25s ease;
}

.chapter-select-btn.chapter-no-exercises .chap-btn-title {
    color: #475569;
}

.chapter-select-btn.chapter-no-exercises .branch-chap-count {
    color: #94a3b8;
    font-size: 0.82rem;
    font-weight: 500;
}

/* Hover effect: Smooth golden-amber highlight signaling introductory / no exercises */
.chapter-select-btn.chapter-no-exercises:hover {
    background-color: #fefce8;
    border-color: #fde047;
    transform: none;
    box-shadow: 0 4px 14px rgba(234, 179, 8, 0.12);
}

.chapter-select-btn.chapter-no-exercises:hover .chap-icon-badge {
    transform: scale(1.06);
    background: #fef08a;
    border-color: #facc15;
    filter: none;
    box-shadow: 0 3px 8px rgba(234, 179, 8, 0.15);
}

/* Tooltip Badge on Right */
.no-ex-hover-badge {
    display: flex;
    align-items: center;
    gap: 0.45rem;
    background: #f1f5f9;
    color: #64748b;
    border: 1px solid #e2e8f0;
    padding: 0.45rem 0.95rem;
    border-radius: 9999px;
    font-size: 0.84rem;
    font-weight: 600;
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    white-space: nowrap;
    flex-shrink: 0;
    margin-left: 0.75rem;
}

.no-ex-hover-badge .no-ex-icon {
    font-size: 0.95rem;
}

.chapter-select-btn.chapter-no-exercises:hover .no-ex-hover-badge {
    background: #fef08a;
    color: #854d0e;
    border-color: #eab308;
    box-shadow: 0 2px 10px rgba(202, 138, 4, 0.22);
    transform: scale(1.04);
}

@media (max-width: 640px) {
    .no-ex-hover-badge {
        padding: 0.3rem 0.6rem;
        font-size: 0.75rem;
    }
}