/* ==============================================================================
   web/style.css
   Style sheets for Calculus 1 SP 2026 Homework Portal
   ============================================================================== */

/* --- Custom Variables & Theme definitions --- */
:root {
    /* Color Tokens - Default Dark Mode */
    --bg-primary: #0b0f19;
    --bg-secondary: #161f30;
    --bg-sidebar: #0e1422;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --accent-blue: #3b82f6;
    --accent-blue-rgb: 59, 130, 246;
    --accent-teal: #0ea5e9;
    --accent-teal-rgb: 14, 165, 233;
    --border-color: #1e293b;
    --card-bg: rgba(22, 31, 48, 0.65);
    --card-border: rgba(255, 255, 255, 0.06);
    --hover-bg: rgba(255, 255, 255, 0.04);
    
    /* Layout Tokens */
    --sidebar-width: 290px;
    --header-height: 70px;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --font-heading: 'Outfit', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-body: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    
    /* Box Shadows */
    --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);
    --shadow-glass: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --shadow-glow: 0 0 15px rgba(59, 130, 246, 0.35);
    --shadow-glow-teal: 0 0 15px rgba(14, 165, 233, 0.35);
}

/* Light Mode Variables Override */
body.light-mode {
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-sidebar: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --accent-blue: #2563eb;
    --accent-blue-rgb: 37, 99, 235;
    --accent-teal: #0891b2;
    --accent-teal-rgb: 8, 145, 178;
    --border-color: #e2e8f0;
    --card-bg: rgba(255, 255, 255, 0.85);
    --card-border: rgba(15, 23, 42, 0.08);
    --hover-bg: rgba(15, 23, 42, 0.03);
    --shadow-glass: 0 8px 32px 0 rgba(148, 163, 184, 0.15);
    --shadow-glow: 0 0 15px rgba(37, 99, 235, 0.18);
    --shadow-glow-teal: 0 0 15px rgba(8, 145, 178, 0.18);
}

/* --- Base & Reset --- */
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: var(--font-body);
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color 0.3s ease, color 0.3s ease;
}

a {
    color: var(--accent-blue);
    text-decoration: none;
    transition: color 0.2s ease;
}

a:hover {
    color: var(--accent-teal);
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    font-weight: 700;
}

/* --- App Layout --- */
.app-container {
    display: flex;
    min-height: 100vh;
}

/* Mobile Header (Hidden on Desktop) */
.mobile-header {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background-color: rgba(var(--bg-sidebar), 0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    z-index: 100;
    padding: 0 1.25rem;
    align-items: center;
    justify-content: space-between;
}

/* Sidebar Styling (Desktop) */
.sidebar {
    width: var(--sidebar-width);
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-color);
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    display: flex;
    flex-direction: column;
    z-index: 90;
    transition: transform 0.3s ease, background-color 0.3s ease;
}

.sidebar-header {
    padding: 2rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.brand {
    display: flex;
    flex-direction: column;
}

.course-code {
    font-size: 0.75rem;
    font-weight: 800;
    letter-spacing: 0.15em;
    color: var(--accent-blue);
    margin-bottom: 0.25rem;
}

.brand-title {
    font-size: 1.8rem;
    font-weight: 800;
    line-height: 1.2;
    color: var(--text-primary);
}

.brand-subtitle {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.sidebar-nav {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem 1rem;
}

.nav-section-title {
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    padding-left: 0.5rem;
}

.pr-list {
    list-style: none;
}

.pr-item {
    margin-bottom: 0.5rem;
}

.pr-link {
    display: flex;
    flex-direction: column;
    padding: 0.85rem 1rem;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s ease;
}

.pr-link:hover {
    background-color: var(--hover-bg);
    color: var(--text-primary);
}

.pr-item.active .pr-link {
    background-color: rgba(var(--accent-blue-rgb), 0.15);
    color: var(--accent-blue);
    border-left: 4px solid var(--accent-blue);
    border-top-left-radius: 0;
    border-bottom-left-radius: 0;
}

.pr-link-num {
    font-size: 0.8rem;
    font-weight: 700;
    text-transform: uppercase;
}

.pr-link-title {
    font-family: var(--font-heading);
    font-size: 0.95rem;
    font-weight: 600;
    margin-top: 0.1rem;
}

.sidebar-footer {
    padding: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.sidebar-action-btn {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background-color: transparent;
    color: var(--text-secondary);
    font-family: var(--font-body);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all 0.2s ease;
    margin-bottom: 1rem;
}

.sidebar-action-btn:hover {
    background-color: var(--hover-bg);
    color: var(--text-primary);
    border-color: var(--text-secondary);
}

.footer-info {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-align: center;
    line-height: 1.4;
}

/* --- Main Content Layout --- */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-width);
    padding: 2.5rem 3rem;
    max-width: 1200px;
    width: calc(100% - var(--sidebar-width));
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Content Header */
.content-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.active-pr-title {
    font-size: 2.2rem;
    font-weight: 800;
    color: var(--text-primary);
}

.active-pr-subtitle {
    font-size: 1rem;
    color: var(--text-secondary);
    margin-top: 0.25rem;
}

.header-actions {
    display: flex;
    gap: 0.75rem;
}

.pdf-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.6rem 1rem;
    border-radius: var(--radius-md);
    background-color: rgba(var(--accent-blue-rgb), 0.1);
    border: 1px solid rgba(var(--accent-blue-rgb), 0.3);
    color: var(--accent-blue);
    font-weight: 600;
    font-size: 0.9rem;
    transition: all 0.2s ease;
}

.pdf-btn:hover {
    background-color: var(--accent-blue);
    color: #ffffff;
    box-shadow: 0 0 10px rgba(var(--accent-blue-rgb), 0.3);
}

.pdf-btn.sol-pdf {
    background-color: rgba(var(--accent-teal-rgb), 0.1);
    border-color: rgba(var(--accent-teal-rgb), 0.3);
    color: var(--accent-teal);
}

.pdf-btn.sol-pdf:hover {
    background-color: var(--accent-teal);
    color: #ffffff;
    box-shadow: 0 0 10px rgba(var(--accent-teal-rgb), 0.3);
}

/* Control Bar (Search, Modes) */
.control-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1.5rem;
    margin-bottom: 2rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--card-border);
    padding: 1rem 1.5rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}

.mode-selector-container {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.control-label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.mode-switch {
    display: flex;
    background-color: rgba(0, 0, 0, 0.2);
    border-radius: var(--radius-md);
    padding: 0.25rem;
    border: 1px solid var(--border-color);
}

.mode-btn {
    border: none;
    background-color: transparent;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    cursor: pointer;
    font-family: var(--font-body);
    font-weight: 500;
    font-size: 0.85rem;
    display: flex;
    align-items: center;
    gap: 0.4rem;
    transition: all 0.2s ease;
}

.mode-btn:hover {
    color: var(--text-primary);
}

.mode-btn.active {
    background-color: var(--accent-blue);
    color: #ffffff;
    box-shadow: var(--shadow-md);
}

.search-container {
    display: flex;
    align-items: center;
    background-color: rgba(0, 0, 0, 0.2);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 0.5rem 1rem;
    width: 320px;
    position: relative;
    transition: border-color 0.2s ease;
}

.search-container:focus-within {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 1px var(--accent-blue);
}

.search-icon {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-right: 0.5rem;
}

.search-container input {
    background: none;
    border: none;
    color: var(--text-primary);
    width: 100%;
    outline: none;
    font-family: var(--font-body);
    font-size: 0.9rem;
}

.search-container input::placeholder {
    color: var(--text-secondary);
}

.clear-search-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1.1rem;
    cursor: pointer;
    padding: 0 0.25rem;
}

.clear-search-btn:hover {
    color: var(--text-primary);
}

/* Tabs for Separate Mode */
.separate-tabs {
    display: flex;
    margin-bottom: 2rem;
    border-bottom: 1px solid var(--border-color);
    gap: 1.5rem;
}

.tab-btn {
    border: none;
    background: none;
    color: var(--text-secondary);
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 600;
    padding: 0.75rem 0.25rem;
    cursor: pointer;
    position: relative;
    transition: color 0.2s ease;
}

.tab-btn:hover {
    color: var(--text-primary);
}

.tab-btn.active {
    color: var(--accent-blue);
}

.tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    right: 0;
    height: 3px;
    background-color: var(--accent-blue);
    border-radius: 3px 3px 0 0;
}

/* --- Content Display Area --- */
.content-display {
    flex: 1;
}

/* Loading & Empty States */
.loading-state, .empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 5rem 2rem;
    text-align: center;
    color: var(--text-secondary);
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid rgba(var(--accent-blue-rgb), 0.1);
    border-top-color: var(--accent-blue);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 1rem;
}

.empty-state-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

/* Topic Sections */
.topic-section {
    margin-bottom: 3.5rem;
}

.topic-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--border-color);
}

.topic-title {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text-primary);
}

.topic-points {
    font-size: 0.85rem;
    font-weight: 600;
    background-color: var(--hover-bg);
    padding: 0.25rem 0.6rem;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

/* Problem & Solution Cards */
.problem-card-wrapper {
    margin-bottom: 2.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

/* Glassmorphism Cards */
.problem-card, .solution-card {
    background-color: var(--card-bg);
    border: 1px solid var(--card-border);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-radius: var(--radius-md);
    padding: 1.5rem 1.8rem;
    box-shadow: var(--shadow-glass);
    transition: box-shadow 0.3s ease, border-color 0.3s ease, transform 0.2s ease;
}

.problem-card {
    border-left: 4px solid var(--accent-blue);
}

.problem-card:hover {
    border-color: rgba(var(--accent-blue-rgb), 0.4);
    box-shadow: var(--shadow-glow);
}

.solution-card {
    border-left: 4px solid var(--accent-teal);
    margin-top: 0.25rem;
}

.solution-card:hover {
    border-color: rgba(var(--accent-teal-rgb), 0.4);
    box-shadow: var(--shadow-glow-teal);
}

/* Pulse highlight animation for cross-referencing */
.problem-card.highlight-pulse {
    animation: highlight-pulse-blue 1.5s ease-out;
}

.solution-card.highlight-pulse {
    animation: highlight-pulse-teal 1.5s ease-out;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.5rem;
}

.card-label {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--accent-blue);
}

.solution-card .card-label {
    color: var(--accent-teal);
}

.card-actions {
    display: flex;
    gap: 0.5rem;
}

/* Card Button Formatting */
.card-btn {
    border: none;
    background: none;
    font-family: var(--font-body);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.4rem 0.75rem;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
}

.card-btn-primary {
    background-color: rgba(var(--accent-blue-rgb), 0.1);
    color: var(--accent-blue);
    border: 1px solid rgba(var(--accent-blue-rgb), 0.2);
}

.card-btn-primary:hover {
    background-color: var(--accent-blue);
    color: #ffffff;
}

.card-btn-teal {
    background-color: rgba(var(--accent-teal-rgb), 0.1);
    color: var(--accent-teal);
    border: 1px solid rgba(var(--accent-teal-rgb), 0.2);
}

.card-btn-teal:hover {
    background-color: var(--accent-teal);
    color: #ffffff;
}

/* Body Contents inside Card */
.card-body {
    font-size: 1rem;
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: auto;
}

/* LaTeX lists rendering styling */
.math-list {
    margin: 0.75rem 0 0.75rem 1.25rem;
    padding-left: 0.5rem;
}

.math-list li {
    margin-bottom: 0.5rem;
}

/* Math typesetting alignments and layouts */
.center-layout {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    margin: 1.25rem 0;
    width: 100%;
}

/* --- Inline Mode Toggle Styles --- */
.inline-toggle-section {
    margin-top: 0.5rem;
}

.solution-collapse {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s cubic-bezier(0, 1, 0, 1);
}

.solution-collapse.open {
    max-height: 2000px;
    transition: max-height 0.8s cubic-bezier(0.9, 0, 0.1, 1);
}

/* --- TikZ Visualiser Styling --- */
.tikz-container {
    width: 100%;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background-color: rgba(255, 255, 255, 0.02);
    border: 1px dashed var(--border-color);
    border-radius: var(--radius-md);
    padding: 1.5rem;
    margin: 1.5rem 0;
    overflow-x: auto;
}

body.light-mode .tikz-container {
    background-color: rgba(0, 0, 0, 0.01);
}

/* SVG sizes styling inside TikZ */
.tikz-container svg {
    max-width: 100% !important;
    height: auto !important;
    display: block;
}

/* Adjust colors in TikZJax rendering for Dark Mode */
body.dark-mode .tikz-container svg {
    /* Filters to invert black lines to white but keep colors legible */
    filter: invert(0.9) hue-rotate(180deg);
}

.tikz-fallback-badge {
    margin-top: 0.75rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
    background-color: var(--hover-bg);
    border: 1px solid var(--border-color);
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-weight: 500;
}

/* --- Keyframe Animations --- */
@keyframes spin {
    to { transform: rotate(360deg); }
}

@keyframes highlight-pulse-blue {
    0% {
        box-shadow: 0 0 0 0 rgba(var(--accent-blue-rgb), 0.7);
        border-color: rgba(var(--accent-blue-rgb), 1);
    }
    70% {
        box-shadow: 0 0 0 15px rgba(var(--accent-blue-rgb), 0);
        border-color: rgba(var(--accent-blue-rgb), 1);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(var(--accent-blue-rgb), 0);
        border-color: var(--card-border);
    }
}

@keyframes highlight-pulse-teal {
    0% {
        box-shadow: 0 0 0 0 rgba(var(--accent-teal-rgb), 0.7);
        border-color: rgba(var(--accent-teal-rgb), 1);
    }
    70% {
        box-shadow: 0 0 0 15px rgba(var(--accent-teal-rgb), 0);
        border-color: rgba(var(--accent-teal-rgb), 1);
    }
    100% {
        box-shadow: 0 0 0 0 rgba(var(--accent-teal-rgb), 0);
        border-color: var(--card-border);
    }
}

/* --- Responsive & Mobile Layout --- */
@media (max-width: 1024px) {
    /* Shrink margins slightly on medium displays */
    .main-content {
        padding: 2rem 2rem;
    }
}

@media (max-width: 768px) {
    /* Toggle Mobile Header */
    .mobile-header {
        display: flex;
    }
    
    .course-code-badge {
        font-size: 0.7rem;
        font-weight: 800;
        background-color: rgba(var(--accent-blue-rgb), 0.15);
        color: var(--accent-blue);
        padding: 0.1rem 0.4rem;
        border-radius: 4px;
        letter-spacing: 0.05em;
        margin-right: 0.5rem;
    }
    
    .mobile-app-title {
        font-family: var(--font-heading);
        font-weight: 800;
        font-size: 1.1rem;
    }
    
    /* Reposition sidebar to offscreen drawer */
    .sidebar {
        transform: translateX(-100%);
        top: var(--header-height);
        z-index: 110;
        box-shadow: var(--shadow-lg);
    }
    
    .sidebar.open {
        transform: translateX(0);
    }
    
    .sidebar-header {
        display: none; /* Hide header inside menu as it's redundant on mobile */
    }
    
    /* Sidebar Overlay */
    .sidebar-overlay {
        display: none;
        position: fixed;
        top: var(--header-height);
        left: 0;
        right: 0;
        bottom: 0;
        background-color: rgba(0, 0, 0, 0.5);
        backdrop-filter: blur(4px);
        z-index: 105;
    }
    
    .sidebar-overlay.visible {
        display: block;
    }
    
    /* Adjust Main Content margins */
    .main-content {
        margin-left: 0;
        width: 100%;
        padding: 1.5rem 1.25rem;
        margin-top: var(--header-height);
    }
    
    /* Content Header styling on mobile */
    .content-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
    
    .active-pr-title {
        font-size: 1.7rem;
    }
    
    /* Control Bar stack on mobile */
    .control-bar {
        flex-direction: column;
        align-items: stretch;
        padding: 1rem;
        gap: 1rem;
    }
    
    .mode-selector-container {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }
    
    .mode-switch {
        width: 100%;
    }
    
    .mode-btn {
        flex: 1;
        justify-content: center;
    }
    
    .search-container {
        width: 100%;
    }
    
    /* Mobile Card adaptations */
    .problem-card, .solution-card {
        padding: 1.25rem 1.25rem;
    }
    
    .card-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.75rem;
    }
    
    .card-actions {
        width: 100%;
    }
    
    .card-btn {
        flex: 1;
        justify-content: center;
    }
    
    .topic-header {
        flex-direction: column;
        gap: 0.5rem;
    }
}

/* Hamburguer Menu Icon Animation */
.menu-toggle {
    background: none;
    border: none;
    width: 24px;
    height: 18px;
    position: relative;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.menu-toggle span {
    display: block;
    width: 100%;
    height: 2.5px;
    background-color: var(--text-primary);
    border-radius: 2px;
    transition: transform 0.25s ease, opacity 0.25s ease;
}

.menu-toggle.open span:nth-child(1) {
    transform: translateY(7.5px) rotate(45deg);
}

.menu-toggle.open span:nth-child(2) {
    opacity: 0;
}

.menu-toggle.open span:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
}