/* ═══════════════════════════════════════════════════════════════════
   THE EDITORIAL — Design System & Component Styles
   A premium dark-themed dashboard for Math OCR
   ═══════════════════════════════════════════════════════════════════ */

/* ── Google Fonts ─────────────────────────────────────────────────── */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&display=swap');

/* ── Design Tokens (CSS Custom Properties) ────────────────────────── */
:root {
    /* Backgrounds */
    --bg-primary: #0F172A;
    --bg-secondary: #1E293B;
    --bg-tertiary: #0F172A;
    --bg-input: #0D1424;
    --bg-sidebar: #1E293B;
    --bg-topnav: #0F172A;
    --bg-card-hover: #253349;

    /* Accent */
    --accent: #3B82F6;
    --accent-hover: #2563EB;
    --accent-glow: rgba(59, 130, 246, 0.15);
    --accent-subtle: rgba(59, 130, 246, 0.08);

    /* Text */
    --text-primary: #F8FAFC;
    --text-secondary: #94A3B8;
    --text-muted: #64748B;
    --text-accent: #3B82F6;

    /* Borders */
    --border: #334155;
    --border-light: #1E293B;
    --border-accent: #3B82F6;

    /* Danger */
    --danger: #EF4444;
    --danger-bg: rgba(239, 68, 68, 0.1);
    --danger-text: #FCA5A5;

    /* Success */
    --success: #22C55E;
    --success-bg: rgba(34, 197, 94, 0.1);
    --success-text: #86EFAC;

    /* Sizing */
    --sidebar-width: 250px;
    --topnav-height: 56px;
    --content-max-width: 900px;
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-xl: 18px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-smooth: 350ms cubic-bezier(0.4, 0, 0.2, 1);

    /* Shadows */
    --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.3), 0 1px 2px rgba(0, 0, 0, 0.2);
    --shadow-card-hover: 0 4px 12px rgba(0, 0, 0, 0.4), 0 2px 4px rgba(0, 0, 0, 0.3);
    --shadow-button: 0 1px 2px rgba(0, 0, 0, 0.3);

    /* Font scale (adjustable via Settings) */
    --font-scale: 1;
}

/* ── High Contrast Mode ───────────────────────────────────────────── */
html.high-contrast {
    --bg-primary: #000000;
    --bg-secondary: #111827;
    --bg-tertiary: #000000;
    --bg-input: #000000;
    --border: #6B7280;
    --text-secondary: #D1D5DB;
    --text-muted: #9CA3AF;
}

/* ── Light Theme (toggled via Settings) ───────────────────────────── */
html.theme-light {
    --bg-primary: #F1F5F9;
    --bg-secondary: #FFFFFF;
    --bg-tertiary: #F1F5F9;
    --bg-input: #E2E8F0;
    --bg-sidebar: #FFFFFF;
    --bg-topnav: #F8FAFC;
    --bg-card-hover: #F1F5F9;
    --text-primary: #0F172A;
    --text-secondary: #475569;
    --text-muted: #94A3B8;
    --border: #CBD5E1;
    --border-light: #E2E8F0;
    --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-card-hover: 0 4px 12px rgba(0, 0, 0, 0.1);
}

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

html {
    font-size: calc(16px * var(--font-scale));
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

a { color: inherit; text-decoration: none; }
button { cursor: pointer; font-family: inherit; }
input, textarea, select { font-family: inherit; }

/* KaTeX overflow control */
.katex-display, .katex {
    overflow-x: auto;
    overflow-y: hidden;
    max-width: 100%;
}
.katex-display > .katex {
    white-space: normal;
}

/* ═══════════════════════════════════════════════════════════════════
   LAYOUT SHELL
   ═══════════════════════════════════════════════════════════════════ */

/* ── Sidebar ──────────────────────────────────────────────────────── */
.sidebar {
    position: fixed;
    top: 0;
    left: -100%; /* Hidden by default on mobile */
    width: 280px;
    height: 100%;
    background: var(--bg-sidebar);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    z-index: 1000;
    padding-top: 0;
    transition: left var(--transition-smooth);
    box-shadow: 4px 0 24px rgba(0, 0, 0, 0.3);
}

.sidebar.open {
    left: 0;
}

@media (min-width: 1025px) {
    .sidebar {
        left: 0;
        width: var(--sidebar-width);
        box-shadow: none;
    }
}

.sidebar-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 999;
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--transition-base), visibility var(--transition-base);
    backdrop-filter: blur(2px);
}

.sidebar-overlay.active {
    opacity: 1;
    visibility: visible;
}

.sidebar-brand {
    padding: 20px 24px;
    font-size: 1.2rem;
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.sidebar-nav {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding: 0 12px;
}

.sidebar-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px; /* Increased tap target for mobile */
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    transition: all var(--transition-fast);
    border: none;
    background: none;
    width: 100%;
    text-align: left;
    position: relative;
    min-height: 44px; /* Accessibility standard */
}

.sidebar-link:hover {
    color: var(--text-primary);
    background: var(--accent-subtle);
}

.sidebar-link.active {
    color: var(--text-accent);
    background: var(--accent-subtle);
}

.sidebar-link.active::before {
    content: '';
    position: absolute;
    left: -12px;
    top: 4px;
    bottom: 4px;
    width: 3px;
    background: var(--accent);
    border-radius: 0 3px 3px 0;
}

.sidebar-link svg {
    width: 18px;
    height: 18px;
    flex-shrink: 0;
}

/* ── Top Navigation Bar ───────────────────────────────────────────── */
.topnav {
    position: fixed;
    top: 0;
    left: 0; /* Full width on mobile */
    right: 0;
    height: var(--topnav-height);
    background: var(--bg-topnav);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: space-between; /* Space for hamburger logic */
    padding: 0 20px; /* Reduced for mobile */
    z-index: 90;
}

@media (min-width: 1025px) {
    .topnav {
        left: var(--sidebar-width);
        padding: 0 32px;
        justify-content: flex-end; /* Top links aligned right */
    }
}

.hamburger-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 8px;
    min-width: 44px;
    min-height: 44px; /* Accessibility tap target */
    margin-left: -8px;
}

@media (min-width: 1025px) {
    .hamburger-btn {
        display: none;
    }
}

.hamburger-btn svg {
    width: 24px;
    height: 24px;
}

.topnav-brand-mobile {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
    display: block;
}

@media (min-width: 1025px) {
    .topnav-brand-mobile {
        display: none;
    }
}

.topnav-links {
    display: none; /* Hidden on mobile */
    gap: 32px;
}

@media (min-width: 1025px) {
    .topnav-links {
        display: flex; /* Show on desktop */
    }
}

.topnav-link {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--text-muted);
    background: none;
    border: none;
    padding: 4px 0;
    transition: color var(--transition-fast);
    position: relative;
    cursor: pointer;
}

.topnav-link:hover {
    color: var(--text-secondary);
}

.topnav-link.active {
    color: var(--text-accent);
}

/* ── Main Content Area ────────────────────────────────────────────── */
.main-content {
    margin-left: 0; /* Base is mobile */
    margin-top: var(--topnav-height);
    min-height: calc(100vh - var(--topnav-height));
    display: flex;
    justify-content: center;
    padding: 24px 16px 80px; /* Base padding for mobile */
}

@media (min-width: 1025px) {
    .main-content {
        margin-left: var(--sidebar-width);
        padding: 40px 40px 80px;
    }
}

.content-wrapper {
    width: 100%;
    max-width: var(--content-max-width);
}

/* ── Page Sections (SPA) ──────────────────────────────────────────── */
.page-section {
    display: none;
    animation: fadeIn 0.3s ease;
}

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

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ═══════════════════════════════════════════════════════════════════
   SHARED COMPONENTS
   ═══════════════════════════════════════════════════════════════════ */

/* ── Page Header ──────────────────────────────────────────────────── */
.page-header {
    margin-bottom: 32px;
}

.page-title {
    font-size: clamp(1.8rem, 5vw + 1rem, 2.5rem);
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.03em;
    line-height: 1.1;
    margin-bottom: 10px;
}

.page-subtitle {
    font-size: clamp(0.85em, 2vw + 0.5rem, 0.95rem);
    color: var(--text-secondary);
    line-height: 1.6;
    max-width: 600px;
}

/* ── Cards ────────────────────────────────────────────────────────── */
.card {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 24px;
    transition: box-shadow var(--transition-base);
}

.card:hover {
    box-shadow: var(--shadow-card-hover);
}

.card-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 6px;
}

.card-title svg {
    width: 18px;
    height: 18px;
    color: var(--text-secondary);
}

.card-subtitle {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 16px;
}

/* ── Buttons ──────────────────────────────────────────────────────── */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 24px;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 600;
    border: none;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn svg {
    width: 16px;
    height: 16px;
}

.btn-primary {
    background: var(--accent);
    color: #FFFFFF;
    box-shadow: var(--shadow-button);
    width: 100%;
}

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-primary:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

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

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

.btn-danger {
    background: var(--danger-bg);
    color: var(--danger);
    border: 1px solid transparent;
}

.btn-danger:hover {
    background: rgba(239, 68, 68, 0.2);
    border-color: var(--danger);
}

.btn-icon {
    width: 34px;
    height: 34px;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    transition: all var(--transition-fast);
}

.btn-icon:hover {
    background: var(--bg-card-hover);
    color: var(--text-primary);
}

.btn-icon.active {
    background: var(--accent);
    color: #FFFFFF;
    border-color: var(--accent);
}

.btn-icon svg {
    width: 16px;
    height: 16px;
}

/* ── Segmented Control ────────────────────────────────────────────── */
.segmented-control {
    display: inline-flex;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 3px;
    gap: 2px;
}

.segment-btn {
    padding: 8px 24px;
    border-radius: calc(var(--radius-md) - 2px);
    font-size: 0.85rem;
    font-weight: 600;
    border: none;
    background: transparent;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

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

.segment-btn.active {
    background: var(--accent);
    color: #FFFFFF;
    box-shadow: 0 1px 3px rgba(59, 130, 246, 0.3);
}

/* ── Toggle Switch ────────────────────────────────────────────────── */
.toggle-switch {
    position: relative;
    width: 48px;
    height: 26px;
    flex-shrink: 0;
}

.toggle-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.toggle-slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: 26px;
    transition: all var(--transition-base);
}

.toggle-slider::before {
    content: '';
    position: absolute;
    height: 20px;
    width: 20px;
    left: 2px;
    bottom: 2px;
    background-color: var(--text-secondary);
    border-radius: 50%;
    transition: all var(--transition-base);
}

.toggle-switch input:checked + .toggle-slider {
    background-color: var(--accent);
    border-color: var(--accent);
}

.toggle-switch input:checked + .toggle-slider::before {
    transform: translateX(22px);
    background-color: #FFFFFF;
}

/* ── Badges / Pills ───────────────────────────────────────────────── */
.badge {
    display: inline-flex;
    align-items: center;
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 0.65rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    text-transform: uppercase;
}

.badge-solved {
    background: rgba(59, 130, 246, 0.15);
    color: #93C5FD;
}

.badge-failed {
    background: rgba(239, 68, 68, 0.15);
    color: #FCA5A5;
}

.badge-format {
    background: var(--bg-tertiary);
    color: var(--text-muted);
    border: 1px solid var(--border);
    font-size: 0.6rem;
    padding: 2px 8px;
}

.badge-latex {
    position: absolute;
    bottom: 10px;
    right: 10px;
    background: var(--bg-secondary);
    color: var(--text-muted);
    border: 1px solid var(--border);
    font-size: 0.6rem;
    font-weight: 700;
    padding: 2px 8px;
    border-radius: 4px;
    letter-spacing: 0.08em;
}

/* ── Form Inputs ──────────────────────────────────────────────────── */
.input-field {
    width: 100%;
    padding: 12px 16px;
    background: var(--bg-input);
    color: var(--text-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    transition: border-color var(--transition-fast);
    outline: none;
}

.input-field:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-glow);
}

.input-field::placeholder {
    color: var(--text-muted);
}

.search-wrapper {
    position: relative;
    flex: 1;
}

.search-wrapper svg {
    position: absolute;
    left: 14px;
    top: 50%;
    transform: translateY(-50%);
    width: 16px;
    height: 16px;
    color: var(--text-muted);
}

.search-wrapper .input-field {
    padding-left: 40px;
}

.select-field {
    padding: 10px 36px 10px 14px;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.8rem;
    font-weight: 500;
    appearance: none;
    -webkit-appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2394A3B8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    cursor: pointer;
    outline: none;
}

.select-field:focus {
    border-color: var(--accent);
}

/* ── Section Labels ───────────────────────────────────────────────── */
.section-label {
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--text-accent);
    letter-spacing: 0.12em;
    text-transform: uppercase;
    margin-bottom: 16px;
}

/* ═══════════════════════════════════════════════════════════════════
   PAGE 1: WORKSPACE
   ═══════════════════════════════════════════════════════════════════ */

.workspace-toggle {
    margin-bottom: 28px;
}

/* ── Handwriting Canvas Card ──────────────────────────────────────── */
.canvas-card {
    margin-bottom: 24px;
}

.canvas-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 12px;
}

.canvas-header-left {
    display: flex;
    align-items: center;
    gap: 10px;
}

.canvas-header-left svg {
    width: 20px;
    height: 20px;
    color: var(--text-secondary);
}

.canvas-toolbar {
    display: flex;
    align-items: center;
    gap: 6px;
}

.toolbar-divider {
    width: 1px;
    height: 20px;
    background: var(--border);
    margin: 0 4px;
}

.dot-size {
    width: auto;
    height: auto;
    border-radius: 50%;
    background: var(--text-muted);
    cursor: pointer;
    transition: all var(--transition-fast);
    border: 2px solid transparent;
    padding: 0;
    display: flex;
    align-items: center;
    justify-content: center;
}

.dot-size.small { width: 8px; height: 8px; }
.dot-size.medium { width: 12px; height: 12px; }
.dot-size.large { width: 16px; height: 16px; }

.dot-size:hover { background: var(--text-secondary); }
.dot-size.active { background: var(--accent); border-color: rgba(59, 130, 246, 0.3); }

.thickness-slider {
    width: 100px;
    height: 4px;
    -webkit-appearance: none;
    appearance: none;
    background: var(--border);
    border-radius: 2px;
    outline: none;
    margin: 0 4px;
}

.thickness-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 14px;
    height: 14px;
    background: var(--text-secondary);
    border-radius: 50%;
    cursor: pointer;
    transition: background var(--transition-fast);
}

.thickness-slider::-webkit-slider-thumb:hover {
    background: var(--accent);
}

.canvas-container {
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--border);
}

#drawingCanvas {
    display: block;
    width: 100%;
    height: 280px;
    background: #FFFFFF;
    cursor: crosshair;
    touch-action: none;
}

/* ── Upload Dropzone ──────────────────────────────────────────────── */
.upload-card {
    margin-bottom: 24px;
}

.dropzone {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 48px 24px;
    border: 2px dashed var(--border);
    border-radius: var(--radius-md);
    transition: all var(--transition-base);
    text-align: center;
    cursor: pointer;
}

.dropzone.drag-over {
    border-color: var(--accent);
    background: var(--accent-subtle);
}

.dropzone-icon {
    width: 64px;
    height: 64px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
}

.dropzone-icon svg {
    width: 28px;
    height: 28px;
    color: var(--text-muted);
}

.dropzone-title {
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.dropzone-text {
    font-size: 0.8rem;
    color: var(--text-secondary);
    max-width: 320px;
    line-height: 1.5;
    margin-bottom: 20px;
}

.dropzone-formats {
    display: flex;
    gap: 8px;
    margin-top: 16px;
}

.upload-preview {
    display: none;
    margin-top: 16px;
    padding: 12px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    align-items: center;
    gap: 12px;
}

.upload-preview.visible {
    display: flex;
}

.upload-preview-name {
    font-size: 0.8rem;
    color: var(--text-secondary);
    flex: 1;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.upload-preview-remove {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 4px;
}

.upload-preview-remove:hover {
    color: var(--danger);
}

/* ── Parse Input Button ───────────────────────────────────────────── */
.parse-action {
    margin-bottom: 32px;
}

/* ── Equation Editor ──────────────────────────────────────────────── */
.equation-editor-card {
    margin-bottom: 8px;
}

.editor-layout {
    display: flex;
    flex-direction: column;
    gap: 20px;
    align-items: stretch;
}

@media (min-width: 1025px) {
    .editor-layout {
        flex-direction: row;
        align-items: flex-start;
    }
}

.editor-textarea-wrapper {
    flex: 1;
    position: relative;
}

/* ── MathQuill Visual Editor ──────────────────────────────────────── */
.mathquill-editor-container {
    position: relative;
}

.mathquill-editor {
    display: block;
    width: 100%;
    min-height: 120px;
    padding: 16px !important;
    font-size: 1.2rem !important;
    cursor: text;
}

/* Dark theme overrides for MathQuill internals */
.mq-editable-field {
    background: var(--bg-input) !important;
    color: var(--text-primary) !important;
    border: 1px solid var(--border) !important;
    border-radius: var(--radius-md) !important;
    box-shadow: none !important;
    transition: border-color var(--transition-fast);
}

.mq-editable-field.mq-focused {
    border-color: var(--accent) !important;
    box-shadow: 0 0 0 3px var(--accent-glow) !important;
}

.mq-editable-field .mq-root-block,
.mq-editable-field .mq-math-mode {
    color: var(--text-primary) !important;
}

.mq-editable-field .mq-cursor {
    border-left-color: var(--accent) !important;
}

.mq-editable-field .mq-selection .mq-matrixed,
.mq-editable-field .mq-selection .mq-matrixed-container,
.mq-editable-field .mq-selection,
.mq-editable-field .mq-selection .mq-non-leaf {
    background: var(--accent-glow) !important;
    color: var(--text-primary) !important;
}

/* MathQuill static math (used in history rendering) */
.mq-static-math {
    color: var(--text-primary) !important;
    border: none !important;
    background: transparent !important;
}

/* Error hint below editor */
.mq-error-hint {
    display: flex;
    align-items: center;
    gap: 6px;
    margin-top: 8px;
    color: var(--danger-text);
    font-size: 0.8rem;
    font-weight: 500;
}

.quick-symbols {
    flex-shrink: 0;
}

.quick-symbols-title {
    font-size: 0.65rem;
    font-weight: 700;
    color: var(--text-muted);
    letter-spacing: 0.12em;
    text-transform: uppercase;
    margin-bottom: 10px;
}

.symbols-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 6px;
}

@media (min-width: 768px) and (max-width: 1024px) {
    .symbols-grid {
        grid-template-columns: repeat(8, 1fr);
    }
}

.symbol-btn {
    width: 48px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 500;
    transition: all var(--transition-fast);
    cursor: pointer;
}

.symbol-btn:hover {
    background: var(--bg-card-hover);
    color: var(--text-primary);
    border-color: var(--accent);
}

.symbol-btn:active {
    transform: scale(0.95);
}

/* ── Solution Result Panel ────────────────────────────────────────── */
.solution-panel {
    margin-top: 24px;
    padding: 24px;
    background: var(--accent-subtle);
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-radius: var(--radius-lg);
    display: none;
}

.solution-panel.visible {
    display: block;
    animation: fadeIn 0.3s ease;
}

.solution-label {
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--accent);
    letter-spacing: 0.1em;
    text-transform: uppercase;
    margin-bottom: 12px;
}

.solution-display {
    font-size: 1.3rem;
    color: var(--text-primary);
    overflow-x: auto;
    padding-bottom: 4px;
}

/* ── Error Message ────────────────────────────────────────────────── */
.error-msg {
    display: none;
    margin-top: 12px;
    padding: 12px 16px;
    background: var(--danger-bg);
    border: 1px solid rgba(239, 68, 68, 0.2);
    border-radius: var(--radius-md);
    color: var(--danger-text);
    font-size: 0.8rem;
    align-items: center;
    gap: 8px;
}

.error-msg.visible {
    display: flex;
}

.error-msg svg {
    width: 16px;
    height: 16px;
    flex-shrink: 0;
}

/* ═══════════════════════════════════════════════════════════════════
   PAGE 2: HISTORY
   ═══════════════════════════════════════════════════════════════════ */

.history-header {
    display: flex;
    flex-direction: column;
    align-items: stretch;
    justify-content: space-between;
    margin-bottom: 28px;
    gap: 16px;
}

@media (min-width: 768px) {
    .history-header {
        flex-direction: row;
        align-items: flex-start;
        gap: 0;
    }
}

.history-header-actions {
    display: flex;
    gap: 10px;
    flex-shrink: 0;
    margin-top: 6px;
}

/* ── Search & Filter Bar ──────────────────────────────────────────── */
.filter-bar {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 28px;
}

@media (min-width: 768px) {
    .filter-bar {
        flex-direction: row;
        flex-wrap: wrap;
    }
}

/* ── History Grid ─────────────────────────────────────────────────── */
.history-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 18px;
    margin-bottom: 32px;
}

@media (min-width: 768px) {
    .history-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (min-width: 1025px) {
    .history-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

.history-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: 20px;
    transition: all var(--transition-base);
    display: flex;
    flex-direction: column;
}

.history-card:hover {
    box-shadow: var(--shadow-card-hover);
    border-color: var(--accent);
}

.history-card-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 14px;
}

.history-type-icon {
    width: 32px;
    height: 32px;
    background: var(--accent-subtle);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.history-type-icon svg {
    width: 16px;
    height: 16px;
    color: var(--accent);
}

.history-type-icon.failed {
    background: var(--danger-bg);
}

.history-type-icon.failed svg {
    color: var(--danger);
}

.history-card-meta {
    flex: 1;
}

.history-type-label {
    font-size: 0.65rem;
    font-weight: 700;
    color: var(--text-secondary);
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.history-timestamp {
    font-size: 0.7rem;
    color: var(--text-muted);
}

.history-card-checkbox {
    width: 16px;
    height: 16px;
    accent-color: var(--accent);
    cursor: pointer;
    display: none;
}

.history-card-checkbox.visible {
    display: block;
}

.history-input-block {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    padding: 16px;
    margin-bottom: 14px;
    font-family: 'Courier New', monospace;
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.5;
    min-height: 80px;
    flex: 1;
    word-break: break-all;
    overflow: hidden;
}

.history-input-block img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    border-radius: var(--radius-sm);
}

.history-result-row {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    gap: 12px;
}

.history-result-label {
    font-size: 0.6rem;
    font-weight: 700;
    color: var(--text-muted);
    letter-spacing: 0.1em;
    text-transform: uppercase;
    margin-bottom: 4px;
}

.history-result-value {
    font-size: 0.85rem;
    color: var(--text-primary);
    word-break: break-all;
}

/* ── Add New Card ─────────────────────────────────────────────────── */
.add-new-card {
    background: transparent;
    border: 2px dashed var(--border);
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 220px;
    cursor: pointer;
    transition: all var(--transition-base);
}

.add-new-card:hover {
    border-color: var(--accent);
    background: var(--accent-subtle);
}

.add-new-icon {
    width: 48px;
    height: 48px;
    border: 2px dashed var(--border);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 12px;
    transition: border-color var(--transition-base);
}

.add-new-card:hover .add-new-icon {
    border-color: var(--accent);
}

.add-new-icon svg {
    width: 20px;
    height: 20px;
    color: var(--text-muted);
}

.add-new-text {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-muted);
    letter-spacing: 0.05em;
}

/* ── History Footer ───────────────────────────────────────────────── */
.history-footer {
    text-align: center;
}

.history-count {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 14px;
}

/* ═══════════════════════════════════════════════════════════════════
   PAGE 3: SETTINGS
   ═══════════════════════════════════════════════════════════════════ */

.settings-section {
    margin-bottom: 36px;
}

.settings-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 18px;
}

@media (min-width: 1025px) {
    .settings-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

.settings-card-wide {
    grid-column: 1 / -1;
}

.settings-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 0;
    border-bottom: 1px solid var(--border-light);
}

.settings-row:last-child {
    border-bottom: none;
}

.settings-row-info {
    flex: 1;
    padding-right: 24px;
}

.settings-row-title {
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.settings-row-subtitle {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.settings-row-control {
    flex-shrink: 0;
    display: flex;
    align-items: center;
    gap: 12px;
}

/* ── Theme Segmented Toggle ───────────────────────────────────────── */
.theme-toggle {
    margin-top: 14px;
}

.theme-segment {
    display: flex;
    align-items: center;
    gap: 6px;
}

.theme-segment svg {
    width: 14px;
    height: 14px;
}

/* ── Font Dropdown ────────────────────────────────────────────────── */
.font-select-wrapper {
    margin-bottom: 14px;
}

.font-select {
    width: 100%;
    padding: 10px 14px;
    background: var(--bg-tertiary);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    appearance: none;
    -webkit-appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2394A3B8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    outline: none;
    cursor: pointer;
}

.font-preview {
    padding: 20px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    text-align: center;
    font-size: 1.1rem;
    color: var(--text-primary);
    min-height: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* ── Scale Slider ─────────────────────────────────────────────────── */
.scale-slider-wrapper {
    display: flex;
    align-items: center;
    gap: 12px;
    width: 260px;
}

.scale-label-small {
    font-size: 0.75rem;
    color: var(--text-muted);
    font-weight: 600;
}

.scale-label-large {
    font-size: 1.2rem;
    color: var(--text-muted);
    font-weight: 600;
}

.scale-slider {
    flex: 1;
    height: 4px;
    -webkit-appearance: none;
    appearance: none;
    background: var(--border);
    border-radius: 2px;
    outline: none;
}

.scale-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 16px;
    height: 16px;
    background: var(--text-secondary);
    border-radius: 50%;
    cursor: pointer;
    transition: background var(--transition-fast);
}

.scale-slider::-webkit-slider-thumb:hover {
    background: var(--accent);
}

/* ═══════════════════════════════════════════════════════════════════
   UTILITY CLASSES
   ═══════════════════════════════════════════════════════════════════ */

.hidden { display: none !important; }
.mt-sm { margin-top: 8px; }
.mt-md { margin-top: 16px; }
.mt-lg { margin-top: 24px; }
.mb-sm { margin-bottom: 8px; }
.mb-md { margin-bottom: 16px; }
.mb-lg { margin-bottom: 24px; }
.gap-sm { gap: 8px; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.text-center { text-align: center; }

/* ── Loading Spinner ──────────────────────────────────────────────── */
.spinner {
    width: 16px;
    height: 16px;
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-top-color: #FFFFFF;
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
    display: inline-block;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ═══════════════════════════════════════════════════════════════════
   RESPONSIVE (LEGACY)
   ═══════════════════════════════════════════════════════════════════ */

/* Replaced by mobile-first min-width media queries above. */

/* ── Scrollbar Styling ────────────────────────────────────────────── */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* ── Solo Delete Button ───────────────────────────────────────────── */
.solo-delete-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    width: 28px;
    height: 28px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0;
    transition: all var(--transition-fast);
    cursor: pointer;
}

.solo-delete-btn svg {
    width: 16px;
    height: 16px;
}

.solo-delete-btn:hover {
    background: var(--danger-bg);
    color: var(--danger);
}

/* ═══════════════════════════════════════════════════════════════════
   MOBILE MATH KEYBOARD
   A fixed-bottom on-screen keyboard for typing equations on mobile.
   Bypasses the native virtual keyboard which MathQuill can't use.
   ═══════════════════════════════════════════════════════════════════ */

.mobile-math-keyboard {
    display: none; /* Hidden on desktop */
}

/* Show only on mobile (<1025px) when workspace page is active */
@media (max-width: 1024px) {
    .mobile-math-keyboard {
        display: block;
        position: fixed;
        bottom: 0;
        left: 0;
        right: 0;
        z-index: 500;
    }
}

/* ── Keyboard Toggle Bar ─────────────────────────────────────────── */
.mkb-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    width: 100%;
    padding: 10px 16px;
    background: var(--bg-secondary);
    border: none;
    border-top: 1px solid var(--border);
    color: var(--accent);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    min-height: 44px;
    transition: background var(--transition-fast);
}

.mkb-toggle:hover {
    background: var(--bg-card-hover);
}

.mkb-toggle svg {
    flex-shrink: 0;
}

/* ── Keyboard Panel (expandable) ─────────────────────────────────── */
.mkb-panel {
    display: none;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border);
    padding: 0;
    max-height: 300px;
    overflow: hidden;
    transition: max-height var(--transition-smooth);
}

.mkb-panel.open {
    display: block;
    animation: slideUpKb 0.25s ease forwards;
}

@keyframes slideUpKb {
    from { opacity: 0; transform: translateY(20px); }
    to   { opacity: 1; transform: translateY(0); }
}

/* ── Tab Row ─────────────────────────────────────────────────────── */
.mkb-tabs {
    display: flex;
    gap: 0;
    border-bottom: 1px solid var(--border);
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.mkb-tab {
    flex: 1;
    min-width: 56px;
    padding: 10px 8px;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-muted);
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
    min-height: 44px;
}

.mkb-tab:hover {
    color: var(--text-secondary);
}

.mkb-tab.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
    background: var(--accent-subtle);
}

/* ── Key Grid ────────────────────────────────────────────────────── */
.mkb-keys {
    padding: 8px;
}

.mkb-grid {
    display: none;
    grid-template-columns: repeat(4, 1fr);
    gap: 6px;
}

.mkb-grid.active {
    display: grid;
}

.mkb-grid-wide {
    /* Functions/structures use fewer, wider buttons */
    grid-template-columns: repeat(3, 1fr);
}

/* ── Individual Key ──────────────────────────────────────────────── */
.mkb-key {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    padding: 8px 4px;
    background: var(--bg-tertiary);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-size: 1.05rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    -webkit-tap-highlight-color: transparent;
    user-select: none;
}

.mkb-key:active {
    background: var(--accent);
    color: #FFFFFF;
    transform: scale(0.94);
    border-color: var(--accent);
}

.mkb-key-wide {
    font-size: 0.85rem;
}

/* ═══════════════════════════════════════════════════════════════════
   VOICE INPUT BUTTON & TRANSCRIPT
   ═══════════════════════════════════════════════════════════════════ */

.voice-input-btn {
    margin-left: auto;
    flex-shrink: 0;
}

.voice-input-btn.listening {
    background: var(--danger);
    color: #FFFFFF;
    border-color: var(--danger);
    animation: voicePulse 1.5s ease-in-out infinite;
}

@keyframes voicePulse {
    0%, 100% { box-shadow: 0 0 0 0 rgba(239, 68, 68, 0.4); }
    50%      { box-shadow: 0 0 0 8px rgba(239, 68, 68, 0); }
}

.voice-transcript {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 16px;
    background: var(--accent-subtle);
    border: 1px solid rgba(59, 130, 246, 0.2);
    border-radius: var(--radius-md);
    margin-bottom: 12px;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.voice-pulse {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background: var(--danger);
    animation: voiceDotPulse 1s ease-in-out infinite;
    flex-shrink: 0;
}

@keyframes voiceDotPulse {
    0%, 100% { opacity: 1; transform: scale(1); }
    50%      { opacity: 0.4; transform: scale(0.7); }
}

/* ═══════════════════════════════════════════════════════════════════
   MOBILE-SPECIFIC OVERRIDES
   ═══════════════════════════════════════════════════════════════════ */

/* Hide the desktop quick-symbols panel on mobile; the math keyboard replaces it */
@media (max-width: 1024px) {
    .desktop-only-symbols {
        display: none !important;
    }

    /* Taller canvas on mobile for finger drawing */
    #drawingCanvas {
        height: 320px;
    }

    /* Add bottom padding so content isn't hidden behind sticky keyboard */
    .main-content {
        padding-bottom: 160px;
    }

    /* Canvas toolbar wrapping on smaller screens */
    .canvas-toolbar {
        flex-wrap: wrap;
        gap: 4px;
    }

    /* Hide thickness slider on small screens to reduce clutter */
    .thickness-slider {
        display: none;
    }

    /* Hide dot-size presets on mobile to declutter */
    .dot-size {
        display: none;
    }

    /* Prevent MathQuill from opening native keyboard on tap */
    .mq-editable-field textarea {
        font-size: 16px !important; /* Prevents iOS zoom */
        opacity: 0 !important;
        position: absolute !important;
        width: 1px !important;
        height: 1px !important;
        pointer-events: none !important;
        user-select: none !important;
        -webkit-user-select: none !important;
    }

    /* Prevent focus outline from showing on hidden textarea */
    .mq-editable-field textarea:focus {
        outline: none !important;
        border: none !important;
        box-shadow: none !important;
    }
    
    /* Ensure the editor itself remains focusable for the cursor to show */
    .mq-editable-field {
        -webkit-tap-highlight-color: transparent;
    }
}