/* ==========================================================================
   AKTU MCA Hub - Complete Stylesheet
   Theme: Light/Dark Modern Academic Portal
   ========================================================================== */

:root {
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --primary-light: #e0e7ff;
    --secondary: #0284c7;
    --secondary-hover: #0369a1;
    --background: #f8fafc;
    --surface: #ffffff;
    --surface-border: #e2e8f0;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --text-inverse: #ffffff;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --primary: #6366f1;
    --primary-hover: #818cf8;
    --primary-light: rgba(99, 102, 241, 0.15);
    --secondary: #38bdf8;
    --secondary-hover: #7dd3fc;
    --background: #0f172a;
    --surface: #1e293b;
    --surface-border: #334155;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 25px -3px rgba(0, 0, 0, 0.5);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: 'Plus Jakarta Sans', sans-serif;
    background-color: var(--background);
    color: var(--text-main);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

a {
    color: var(--primary);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    color: var(--primary-hover);
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    outline: none;
}

/* ================= HEADER & NAV ================= */
.header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--surface);
    border-bottom: 1px solid var(--surface-border);
    box-shadow: var(--shadow-sm);
    backdrop-filter: blur(8px);
}

.nav-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0.8rem 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1.5rem;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    text-decoration: none;
}

.logo-icon {
    font-size: 1.8rem;
    color: var(--primary);
}

.logo-text {
    display: flex;
    flex-direction: column;
}

.logo-title {
    font-family: 'Space Grotesk', sans-serif;
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--text-main);
    line-height: 1.2;
}

.badge-tag {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: white;
    font-size: 0.65rem;
    padding: 2px 6px;
    border-radius: 4px;
    vertical-align: middle;
}

.logo-sub {
    font-size: 0.725rem;
    color: var(--text-muted);
}

.header-search {
    position: relative;
    flex: 1;
    max-width: 380px;
}

.header-search input {
    width: 100%;
    padding: 0.55rem 1rem 0.55rem 2.4rem;
    border-radius: 20px;
    border: 1px solid var(--surface-border);
    background-color: var(--background);
    color: var(--text-main);
    font-size: 0.875rem;
    transition: var(--transition);
}

.header-search input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-light);
    outline: none;
}

.search-icon {
    position: absolute;
    left: 0.85rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    font-size: 0.875rem;
}

.search-dropdown {
    position: absolute;
    top: 110%;
    left: 0;
    right: 0;
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    max-height: 350px;
    overflow-y: auto;
    display: none;
    z-index: 1000;
}

.search-dropdown.active {
    display: block;
}

.search-item {
    padding: 0.75rem 1rem;
    border-bottom: 1px solid var(--surface-border);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.search-item:hover {
    background-color: var(--primary-light);
}

.nav-links {
    display: flex;
    gap: 1.25rem;
}

.nav-link {
    color: var(--text-muted);
    font-weight: 600;
    font-size: 0.9rem;
    padding: 0.4rem 0.2rem;
    border-bottom: 2px solid transparent;
}

.nav-link:hover, .nav-link.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.icon-btn {
    background: var(--background);
    border: 1px solid var(--surface-border);
    color: var(--text-main);
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

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

.mobile-toggle {
    display: none;
    background: transparent;
    font-size: 1.25rem;
    color: var(--text-main);
}

/* ================= HERO SECTION ================= */
.main-content {
    max-width: 1280px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    min-height: calc(100vh - 250px);
}

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease-in-out;
}

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

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

.hero {
    text-align: center;
    padding: 3rem 1rem 2rem;
    max-width: 850px;
    margin: 0 auto;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 700;
    font-size: 0.825rem;
    padding: 0.35rem 1rem;
    border-radius: 20px;
    margin-bottom: 1.25rem;
}

.hero-title {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 3rem;
    font-weight: 800;
    line-height: 1.15;
    margin-bottom: 1.25rem;
}

.text-gradient {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-subtitle {
    font-size: 1.125rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.hero-cta {
    display: flex;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
    margin-bottom: 3rem;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
}

.btn-primary {
    background-color: var(--primary);
    color: white;
    box-shadow: 0 4px 12px rgba(79, 70, 229, 0.3);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    color: white;
    transform: translateY(-2px);
}

.btn-secondary {
    background-color: var(--surface);
    color: var(--text-main);
    border: 1px solid var(--surface-border);
}

.btn-secondary:hover {
    background-color: var(--primary-light);
    color: var(--primary);
    transform: translateY(-2px);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1.25rem;
    margin-top: 1.5rem;
}

.stat-card {
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    box-shadow: var(--shadow-sm);
}

.stat-icon {
    width: 48px;
    height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    color: white;
}

.bg-blue { background: linear-gradient(135deg, #3b82f6, #1d4ed8); }
.bg-purple { background: linear-gradient(135deg, #8b5cf6, #6d28d9); }
.bg-indigo { background: linear-gradient(135deg, #6366f1, #4338ca); }
.bg-sky { background: linear-gradient(135deg, #0ea5e9, #0369a1); }

.stat-info {
    display: flex;
    flex-direction: column;
    text-align: left;
}

.stat-num {
    font-weight: 800;
    font-size: 1.4rem;
    line-height: 1;
}

.stat-label {
    font-size: 0.775rem;
    color: var(--text-muted);
}

/* ================= GRID & CARDS ================= */
.section-container {
    margin-top: 3.5rem;
}

.section-header {
    text-align: center;
    margin-bottom: 2rem;
}

.section-header h2 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 1.85rem;
    margin-bottom: 0.4rem;
}

.section-header p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

.grid-4 { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1.5rem; }
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(310px, 1fr)); gap: 1.5rem; }
.grid-2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(450px, 1fr)); gap: 1.5rem; }
.grid-1 { display: flex; flex-direction: column; gap: 1.25rem; }

.card {
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    transition: var(--transition);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

.sem-card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.sem-badge {
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 700;
    font-size: 0.75rem;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
}

.card-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.card-desc {
    color: var(--text-muted);
    font-size: 0.875rem;
    margin-bottom: 1.25rem;
}

.card-link {
    font-weight: 700;
    font-size: 0.9rem;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

/* Official AKTU Banner */
.aktu-banner {
    background: linear-gradient(135deg, var(--surface), var(--primary-light));
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-lg);
    padding: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1.5rem;
}

.aktu-banner-content h3 {
    font-size: 1.35rem;
    margin-bottom: 0.3rem;
}

.aktu-banner-content p {
    color: var(--text-muted);
    font-size: 0.9rem;
}

.aktu-links {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.aktu-link-btn {
    background: var(--surface);
    color: var(--text-main);
    border: 1px solid var(--surface-border);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    font-weight: 600;
}

.aktu-link-btn:hover {
    background: var(--primary);
    color: white;
}

/* ================= PAGE HEADERS & FILTERS ================= */
.page-header {
    margin-bottom: 2rem;
}

.page-header h1 {
    font-family: 'Space Grotesk', sans-serif;
    font-size: 2.25rem;
    margin-bottom: 0.3rem;
}

.page-header p {
    color: var(--text-muted);
}

.filter-card {
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    box-shadow: var(--shadow-sm);
}

.filter-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1rem;
}

.filter-grid-2 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1rem;
}

.filter-group {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.filter-group label {
    font-size: 0.8rem;
    font-weight: 700;
    color: var(--text-muted);
}

.filter-group select, .filter-group input {
    padding: 0.6rem 0.8rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--surface-border);
    background: var(--background);
    color: var(--text-main);
    font-size: 0.9rem;
    outline: none;
}

.filter-group select:focus, .filter-group input:focus {
    border-color: var(--primary);
}

/* ================= TABLES ================= */
.table-responsive {
    overflow-x: auto;
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
}

.data-table {
    width: 100%;
    border-collapse: collapse;
    text-align: left;
}

.data-table th, .data-table td {
    padding: 1rem 1.25rem;
    border-bottom: 1px solid var(--surface-border);
}

.data-table th {
    background-color: var(--background);
    font-weight: 700;
    font-size: 0.85rem;
    color: var(--text-muted);
    text-transform: uppercase;
}

.data-table tbody tr:hover {
    background-color: var(--primary-light);
}

.code-badge {
    font-family: monospace;
    background: var(--background);
    padding: 2px 6px;
    border-radius: 4px;
    border: 1px solid var(--surface-border);
    font-size: 0.85rem;
}

/* ================= SEMESTER PILLS NAV ================= */
.sem-pills-nav {
    display: flex;
    gap: 0.5rem;
    border-bottom: 2px solid var(--surface-border);
    padding-bottom: 0.5rem;
    overflow-x: auto;
}

.sem-pill {
    padding: 0.6rem 1.25rem;
    border-radius: var(--radius-sm);
    background: transparent;
    color: var(--text-muted);
    font-weight: 600;
    white-space: nowrap;
}

.sem-pill.active {
    background: var(--primary);
    color: white;
}

.subject-card-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid var(--surface-border);
}

.sub-action-btn {
    font-size: 0.775rem;
    padding: 0.35rem 0.65rem;
    border-radius: 6px;
    background: var(--background);
    border: 1px solid var(--surface-border);
    color: var(--text-main);
    font-weight: 600;
}

.sub-action-btn:hover {
    background: var(--primary-light);
    color: var(--primary);
}

/* ================= NOTES LAYOUT ================= */
.notes-wrapper {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 1.5rem;
}

.notes-sidebar {
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    height: fit-content;
}

.sidebar-title {
    font-size: 1rem;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--surface-border);
}

.notes-sub-list {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.notes-sub-item {
    padding: 0.6rem 0.8rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-muted);
    transition: var(--transition);
}

.notes-sub-item:hover, .notes-sub-item.active {
    background: var(--primary-light);
    color: var(--primary);
}

.notes-main {
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
    padding: 1.75rem;
}

.topic-accordion {
    border: 1px solid var(--surface-border);
    border-radius: var(--radius-md);
    margin-bottom: 1rem;
    overflow: hidden;
}

.topic-header {
    background: var(--background);
    padding: 1rem 1.25rem;
    font-weight: 700;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.topic-body {
    padding: 1.25rem;
    border-top: 1px solid var(--surface-border);
    display: none;
    background: var(--surface);
}

.topic-accordion.open .topic-body {
    display: block;
}

/* ================= IMPORTANT QUESTIONS ================= */
.imp-card {
    background: var(--surface);
    border: 1px solid var(--surface-border);
    border-left: 4px solid var(--primary);
    border-radius: var(--radius-md);
    padding: 1.25rem;
}

.imp-header {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    margin-bottom: 0.75rem;
}

.imp-tags {
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.tag {
    font-size: 0.7rem;
    font-weight: 700;
    padding: 2px 8px;
    border-radius: 12px;
    text-transform: uppercase;
}

.tag-unit { background: #e0f2fe; color: #0369a1; }
.tag-easy { background: #dcfce7; color: #15803d; }
.tag-med { background: #fef3c7; color: #b45309; }
.tag-hard { background: #ffe4e6; color: #be123c; }

.imp-q-text {
    font-size: 1.05rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
}

.answer-toggle-btn {
    background: transparent;
    color: var(--primary);
    font-weight: 700;
    font-size: 0.85rem;
    padding: 0;
}

.answer-box {
    margin-top: 1rem;
    padding: 1rem;
    background: var(--background);
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    display: none;
    border-left: 3px solid var(--secondary);
}

/* ================= MODAL & TOAST ================= */
.modal {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.6);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 2000;
    padding: 1rem;
}

.modal.active { display: flex; }

.modal-content {
    background: var(--surface);
    border-radius: var(--radius-lg);
    width: 100%;
    max-width: 650px;
    box-shadow: var(--shadow-lg);
    overflow: hidden;
}

.modal-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--surface-border);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-close {
    font-size: 1.5rem;
    background: none;
    color: var(--text-muted);
}

.modal-body {
    padding: 2rem 1.5rem;
}

.pdf-placeholder-box {
    text-align: center;
    padding: 2rem;
    background: var(--background);
    border: 2px dashed var(--surface-border);
    border-radius: var(--radius-md);
}

.pdf-big-icon {
    font-size: 3.5rem;
    color: #ef4444;
    margin-bottom: 1rem;
}

.pdf-sim-meta {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    margin-top: 1rem;
    font-size: 0.8rem;
    color: var(--text-muted);
}

.modal-footer {
    padding: 1rem 1.5rem;
    background: var(--background);
    border-top: 1px solid var(--surface-border);
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}

.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: #10b981;
    color: white;
    padding: 0.8rem 1.25rem;
    border-radius: var(--radius-sm);
    font-weight: 600;
    box-shadow: var(--shadow-lg);
    transform: translateY(150%);
    transition: transform 0.3s ease;
    z-index: 3000;
}

.toast.show {
    transform: translateY(0);
}

/* ================= FOOTER ================= */
.footer {
    background-color: #0f172a;
    color: #94a3b8;
    padding: 4rem 1.5rem 2rem;
    margin-top: 5rem;
    border-top: 1px solid #1e293b;
}

.footer-container {
    max-width: 1280px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 2fr repeat(3, 1fr);
    gap: 2.5rem;
}

.footer h4 {
    color: #f8fafc;
    font-size: 1rem;
    margin-bottom: 1.25rem;
}

.footer ul {
    list-style: none;
}

.footer ul li {
    margin-bottom: 0.6rem;
}

.footer ul a {
    color: #94a3b8;
    font-size: 0.875rem;
}

.footer ul a:hover {
    color: #38bdf8;
}

.text-red { color: #ef4444; }
.copyright { font-size: 0.8rem; margin-top: 1.5rem; color: #64748b; }
.text-sm { font-size: 0.85rem; }
.mt-4 { margin-top: 1rem; }
.mt-6 { margin-top: 1.5rem; }
.mt-8 { margin-top: 2rem; }

/* ================= RESPONSIVE ================= */
@media (max-width: 900px) {
    .notes-wrapper { grid-template-columns: 1fr; }
    .footer-container { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--surface);
        flex-direction: column;
        padding: 1.5rem;
        border-bottom: 1px solid var(--surface-border);
        box-shadow: var(--shadow-lg);
    }
    .nav-links.mobile-active { display: flex; }
    .mobile-toggle { display: block; }
    .header-search { max-width: 180px; }
    .hero-title { font-size: 2.2rem; }
    .footer-container { grid-template-columns: 1fr; }
}