/**
 * J-ALGO Capital - Dedicated Concepts Library Page Styles
 * Sleek, modern, high-contrast dark quant aesthetic.
 */

:root {
    --concept-bg: #0d1520;
    --concept-card: rgba(15, 23, 33, 0.85);
    --concept-card-hover: rgba(20, 32, 45, 0.95);
    --concept-teal: #2dd4bf;
    --concept-teal-dim: rgba(45, 212, 191, 0.08);
    --concept-border: rgba(255, 255, 255, 0.07);
    --concept-border-hover: rgba(255, 255, 255, 0.16);
    --concept-text: #f0f4f8;
    --concept-text-muted: rgba(230, 230, 230, 0.48);
    --concept-text-sec: rgba(230, 230, 230, 0.75);
    --concept-mono: 'JetBrains Mono', 'Fira Code', ui-monospace, Menlo, monospace;
}

/* Loading state while dataset streams in */
.concepts-loading {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    min-height: 40vh;
    color: var(--concept-text-muted);
    font-family: var(--concept-mono);
    font-size: 0.85rem;
}

.concepts-loading-spinner {
    width: 34px;
    height: 34px;
    border: 3px solid rgba(45, 212, 191, 0.15);
    border-top-color: var(--concept-teal);
    border-radius: 50%;
    animation: concepts-spin 0.8s linear infinite;
}

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

/* Page Layout */
.concepts-page-body {
    background-color: var(--concept-bg);
    background-image: 
        radial-gradient(circle at 50% -5%, rgba(20, 145, 115, 0.26) 0%, transparent 65%),
        radial-gradient(circle at 100% 45%, rgba(20, 180, 140, 0.12) 0%, transparent 55%),
        radial-gradient(circle at 0% 75%, rgba(45, 212, 191, 0.08) 0%, transparent 45%),
        linear-gradient(180deg, rgba(16, 26, 38, 0.5) 0%, rgba(10, 16, 24, 0.85) 100%);
    background-attachment: fixed;
    color: var(--concept-text);
    min-height: 100vh;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    line-height: 1.5;
    overflow-x: hidden;
}

.concepts-navbar {
    position: sticky;
    top: 0;
    z-index: 100;
    height: 64px;
    background: rgba(7, 10, 14, 0.88);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--concept-border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 2rem;
}

.concepts-nav-brand {
    display: flex;
    align-items: center;
    gap: 1rem;
    text-decoration: none;
}

.concepts-nav-brand img {
    height: 34px;
    width: auto;
    border-radius: 8px;
}

.concepts-badge-pill {
    font-family: var(--concept-mono);
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: #94a3b8;
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid rgba(255, 255, 255, 0.08);
    padding: 0.25rem 0.65rem;
    border-radius: 999px;
}

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

.btn-nav-home {
    color: var(--concept-text-sec);
    text-decoration: none;
    font-size: 0.82rem;
    transition: color 0.2s ease;
}

.btn-nav-home:hover {
    color: #ffffff;
}

.btn-home-text-short {
    display: none;
}

/* Page Hero */
.concepts-page-header {
    max-width: 1360px;
    margin: 0 auto;
    padding: 2.2rem 1.5rem 1rem;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    flex-wrap: wrap;
    gap: 1.5rem;
}

.concepts-header-left h1 {
    font-size: clamp(2rem, 3.5vw, 2.8rem);
    font-weight: 800;
    letter-spacing: -0.03em;
    line-height: 1.15;
    margin-bottom: 0.5rem;
    background: linear-gradient(180deg, #ffffff 40%, rgba(240, 244, 248, 0.7) 100%);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.concepts-header-left p {
    font-size: 0.95rem;
    color: var(--concept-text-sec);
    max-width: 720px;
    line-height: 1.6;
}

.concepts-header-stats {
    display: flex;
    align-items: center;
    gap: 1.25rem;
    background: rgba(13, 21, 28, 0.7);
    border: 1px solid var(--concept-border);
    padding: 0.75rem 1.25rem;
    border-radius: 12px;
}

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat-item-num {
    font-family: var(--concept-mono);
    font-size: 1.35rem;
    font-weight: 800;
    color: var(--concept-teal);
    line-height: 1.2;
}

.stat-item-lbl {
    font-size: 0.65rem;
    color: var(--concept-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    font-weight: 600;
}

/* Main Section Tabs Switcher */
.concepts-section-tabs {
    max-width: 1360px;
    margin: 1.75rem auto 1.25rem;
    padding: 0 1.5rem;
    width: 100%;
    box-sizing: border-box;
}

.section-tabs-bar {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 0.5rem;
    background: rgba(10, 16, 22, 0.85);
    border: 1px solid var(--concept-border);
    border-radius: 12px;
    padding: 0.35rem;
    width: 100%;
    box-sizing: border-box;
}

.btn-section-tab {
    background: transparent;
    border: none;
    color: var(--concept-text-sec);
    font-family: inherit;
    font-size: 0.84rem;
    font-weight: 500;
    padding: 0.55rem 0.65rem;
    border-radius: 8px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.45rem;
    white-space: nowrap;
    transition: all 0.2s ease;
    width: 100%;
    box-sizing: border-box;
    min-width: 0;
}

.btn-section-tab span:first-child {
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.btn-section-tab:hover {
    color: var(--concept-text);
    background: rgba(255, 255, 255, 0.04);
}

.btn-section-tab.active {
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.16);
    color: #ffffff;
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
}

.tab-count-badge {
    font-family: var(--concept-mono);
    font-size: 0.68rem;
    padding: 0.12rem 0.45rem;
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.06);
    color: #64748b;
    font-weight: 600;
    flex-shrink: 0;
    transition: all 0.2s ease;
}

.btn-section-tab.active .tab-count-badge {
    background: rgba(45, 212, 191, 0.14);
    color: #2dd4bf;
}

.btn-section-tab:not(.active) .tab-count-badge {
    background: rgba(255, 255, 255, 0.05);
    color: #64748b;
}

@media (max-width: 1080px) {
    .section-tabs-bar {
        grid-template-columns: repeat(2, 1fr);
    }
}

.badge-pending {
    font-family: var(--concept-mono);
    font-size: 0.65rem;
    font-weight: 600;
    text-transform: uppercase;
    color: #fbbf24;
    background: rgba(245, 158, 11, 0.12);
    border: 1px solid rgba(245, 158, 11, 0.3);
    padding: 0.15rem 0.5rem;
    border-radius: 4px;
}

/* Filter & Search Bar */
.concepts-filter-bar {
    max-width: 1360px;
    margin: 0 auto 1.5rem;
    padding: 0 1.5rem;
}

.filter-bar-inner {
    background: rgba(10, 16, 22, 0.9);
    border: 1px solid var(--concept-border);
    border-radius: 14px;
    padding: 0.85rem 1rem;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    backdrop-filter: blur(12px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.35);
}

.filter-top-row {
    display: flex;
    align-items: center;
    gap: 0.85rem;
    flex-wrap: wrap;
}

.search-input-box {
    position: relative;
    flex: 1;
    min-width: 0;
}

.search-icon-svg {
    position: absolute;
    left: 0.9rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--concept-text-muted);
    pointer-events: none;
}

.concept-search-field {
    width: 100%;
    height: 42px;
    background: rgba(15, 23, 31, 0.95);
    border: 1px solid rgba(255, 255, 255, 0.09);
    border-radius: 8px;
    padding: 0 2.5rem 0 2.5rem;
    color: var(--concept-text);
    font-size: 0.88rem;
    font-family: inherit;
    transition: all 0.2s ease;
}

.concept-search-field:focus {
    outline: none;
    border-color: rgba(45, 212, 191, 0.45);
    box-shadow: 0 0 0 3px rgba(45, 212, 191, 0.08);
}

.search-clear-cross {
    position: absolute;
    right: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    background: transparent;
    border: none;
    color: var(--concept-text-muted);
    cursor: pointer;
    font-size: 0.9rem;
    padding: 0.2rem;
    display: none;
}

.search-clear-cross:hover {
    color: var(--concept-teal);
}

.filter-dropdown {
    height: 42px;
    padding: 0 2rem 0 0.85rem;
    background: rgba(15, 23, 31, 0.95);
    border: 1px solid var(--concept-border);
    border-radius: 8px;
    color: var(--concept-text);
    font-size: 0.82rem;
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%2394a3b8' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 0.75rem center;
    background-size: 13px;
    min-width: 180px;
    max-width: 280px;
}

.filter-dropdown:focus {
    outline: none;
    border-color: rgba(45, 212, 191, 0.4);
}

.view-mode-group {
    display: flex;
    align-items: center;
    background: rgba(15, 23, 31, 0.95);
    border: 1px solid var(--concept-border);
    border-radius: 8px;
    padding: 0.15rem;
}

.view-mode-btn {
    background: transparent;
    border: none;
    color: var(--concept-text-muted);
    padding: 0.4rem 0.6rem;
    border-radius: 6px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.35rem;
    font-size: 0.75rem;
    transition: all 0.2s ease;
}

.view-mode-btn.active {
    background: rgba(255, 255, 255, 0.08);
    color: #ffffff;
    font-weight: 600;
}

.filter-tags-row {
    display: flex;
    align-items: center;
    gap: 0.45rem;
    overflow-x: auto;
    padding-bottom: 0.2rem;
}

.filter-tag-pill {
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(255, 255, 255, 0.08);
    color: var(--concept-text-sec);
    padding: 0.25rem 0.65rem;
    border-radius: 999px;
    font-size: 0.72rem;
    cursor: pointer;
    white-space: nowrap;
    transition: all 0.2s ease;
}

.filter-tag-pill:hover {
    color: var(--concept-text);
    border-color: rgba(255, 255, 255, 0.2);
}

.filter-tag-pill.active {
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(45, 212, 191, 0.35);
    color: #5eead4;
    font-weight: 600;
}

/* Concepts Count Header */
.concepts-meta-strip {
    max-width: 1360px;
    margin: 0 auto 1.25rem;
    padding: 0 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.82rem;
    color: var(--concept-text-muted);
}

.concepts-meta-strip b {
    color: #cbd5e1;
    font-family: var(--concept-mono);
}

/* Concept Cards Grid */
.concepts-cards-grid {
    max-width: 1360px;
    margin: 0 auto 3rem;
    padding: 0 1.5rem;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(min(100%, 340px), 1fr));
    gap: 1.25rem;
}

.concept-item-card {
    background: var(--concept-card);
    border: 1px solid var(--concept-border);
    border-radius: 12px;
    padding: 1.4rem;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    backdrop-filter: blur(14px);
    cursor: pointer;
    position: relative;
}

.concept-item-card:hover {
    background: var(--concept-card-hover);
    border-color: var(--concept-border-hover);
    transform: translateY(-3px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
}

.card-top-strip {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 0.75rem;
    gap: 0.5rem;
}

.card-badges {
    display: flex;
    align-items: center;
    gap: 0.45rem;
    flex-wrap: wrap;
}

.badge-group {
    font-family: var(--concept-mono);
    font-size: 0.65rem;
    font-weight: 700;
    padding: 0.12rem 0.45rem;
    border-radius: 4px;
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid rgba(255, 255, 255, 0.08);
    color: #94a3b8;
    text-transform: uppercase;
}

.badge-category {
    font-size: 0.65rem;
    padding: 0.12rem 0.5rem;
    border-radius: 4px;
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid rgba(255, 255, 255, 0.08);
    color: var(--concept-text-sec);
    max-width: 220px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.card-concept-title {
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--concept-text);
    margin-bottom: 0.45rem;
    line-height: 1.35;
    transition: color 0.2s ease;
}

.concept-item-card:hover .card-concept-title {
    color: var(--concept-teal);
}

/* pt1.txt Summary Row */
.card-pt1-summary {
    background: rgba(255, 255, 255, 0.025);
    border-left: 2px solid rgba(45, 212, 191, 0.5);
    padding: 0.45rem 0.75rem;
    border-radius: 0 4px 4px 0;
    font-size: 0.8rem;
    color: var(--concept-text);
    margin-bottom: 0.85rem;
    line-height: 1.4;
}

.card-pt1-summary b {
    color: #94a3b8;
    font-weight: 600;
    font-family: var(--concept-mono);
    font-size: 0.72rem;
    text-transform: uppercase;
    display: block;
    margin-bottom: 0.15rem;
}

.card-overview-text {
    font-size: 0.84rem;
    color: var(--concept-text-sec);
    line-height: 1.5;
    margin-bottom: 0.85rem;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* Formula Block */
.card-math-box {
    background: rgba(6, 10, 14, 0.85);
    border: 1px solid rgba(255, 255, 255, 0.06);
    border-radius: 6px;
    padding: 0.65rem 0.85rem;
    margin-bottom: 0.85rem;
    font-family: var(--concept-mono);
    font-size: 0.76rem;
    color: #e2e8f0;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.card-math-box-label {
    font-size: 0.62rem;
    color: var(--concept-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: 0.2rem;
}

/* Coordinate Variable Box */
.card-coord-vars {
    background: rgba(6, 10, 14, 0.85);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 6px;
    padding: 0.55rem 0.85rem;
    margin-bottom: 0.85rem;
    font-family: var(--concept-mono);
    font-size: 0.82rem;
    color: #e2e8f0;
}

.card-coord-body {
    font-size: 0.82rem;
    color: var(--concept-text-sec);
    line-height: 1.5;
    margin-bottom: 0.85rem;
}

/* Intuition / Analogy Callout */
.card-intuition-callout {
    background: rgba(255, 255, 255, 0.025);
    border: 1px dashed rgba(255, 255, 255, 0.12);
    border-radius: 6px;
    padding: 0.65rem 0.85rem;
    font-size: 0.78rem;
    color: #cbd5e1;
    font-style: italic;
    line-height: 1.45;
    margin-bottom: 0.85rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* Card Bottom */
.card-bottom-strip {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 0.75rem;
    border-top: 1px solid rgba(255, 255, 255, 0.05);
}

.btn-read-more {
    background: transparent;
    border: none;
    color: var(--concept-teal);
    font-size: 0.8rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.35rem;
    cursor: pointer;
    transition: gap 0.2s ease;
}

.concept-item-card:hover .btn-read-more {
    gap: 0.55rem;
}

.card-source-tag {
    font-family: var(--concept-mono);
    font-size: 0.68rem;
    color: var(--concept-text-muted);
}

/* Table View */
.concepts-table-wrap {
    max-width: 1360px;
    margin: 0 auto 3rem;
    padding: 0 1.5rem;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.concepts-flat-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--concept-card);
    border: 1px solid var(--concept-border);
    border-radius: 12px;
    overflow: hidden;
    font-size: 0.85rem;
}

.concepts-flat-table th {
    background: rgba(10, 16, 22, 0.95);
    padding: 0.85rem 1rem;
    text-align: left;
    font-size: 0.72rem;
    text-transform: uppercase;
    color: var(--concept-text-muted);
    font-weight: 700;
    letter-spacing: 0.06em;
    border-bottom: 1px solid var(--concept-border);
    white-space: nowrap;
}

.concepts-flat-table td {
    padding: 0.85rem 1rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.03);
    color: var(--concept-text-sec);
    vertical-align: middle;
}

.concepts-flat-table tr:hover td {
    background: rgba(255, 255, 255, 0.03);
    color: var(--concept-text);
}

/* Modal Dossier */
#modal-inner-container {
    /* Flex item of the backdrop: must be allowed to shrink below the
       intrinsic width of modal content, otherwise a long unbroken
       formula/params token forces the window off-screen. */
    min-width: 0;
    width: 100%;
    max-width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}

.concept-modal-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(4, 7, 10, 0.85);
    backdrop-filter: blur(10px);
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1.5rem;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.25s ease;
}

.concept-modal-backdrop.open {
    opacity: 1;
    pointer-events: auto;
}

.concept-modal-window {
    background: #090e13;
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 14px;
    width: 100%;
    max-width: 860px;
    min-width: 0;
    /* Children can never inflate this box's intrinsic size — hard guarantee
       that the window never exceeds the viewport on any device. */
    contain: inline-size;
    max-height: 90vh;
    max-height: 90svh;
    display: flex;
    flex-direction: column;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.85), 0 0 1px rgba(255, 255, 255, 0.1);
    transform: scale(0.96) translateY(12px);
    transition: transform 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    overflow: hidden;
}

.concept-modal-backdrop.open .concept-modal-window {
    transform: scale(1) translateY(0);
}

.concept-modal-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
    background: rgba(12, 19, 25, 0.7);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 1rem;
    min-width: 0;
    /* Never compress the header — keeps the close button visible
       even when modal content is very tall. */
    flex-shrink: 0;
}

.concept-modal-breadcrumbs {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.78rem;
    min-width: 0;
    flex-wrap: wrap;
}

.concept-modal-nav-btns {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    flex-shrink: 0;
    margin-left: auto;
}

.btn-nav-modal {
    background: rgba(255, 255, 255, 0.04);
    border: 1px solid rgba(255, 255, 255, 0.08);
    color: var(--concept-text-sec);
    padding: 0.35rem 0.65rem;
    border-radius: 6px;
    font-size: 0.75rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-nav-modal:hover:not(:disabled) {
    color: var(--concept-teal);
    border-color: var(--concept-teal);
}

.btn-nav-modal:disabled {
    opacity: 0.35;
    cursor: not-allowed;
}

.btn-close-modal {
    background: transparent;
    border: none;
    color: var(--concept-text-muted);
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    transition: all 0.2s ease;
}

.btn-close-modal:hover {
    color: #ff5274;
}

.concept-modal-scroll {
    padding: 1.75rem;
    overflow-y: auto;
    overflow-x: hidden;
    overflow-wrap: anywhere;
    min-width: 0;
    flex: 1;
}

.modal-section-h3 {
    font-size: 0.76rem;
    font-family: var(--concept-mono);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: #94a3b8;
    margin: 1.5rem 0 0.6rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.modal-section-h3::after {
    content: '';
    flex: 1;
    height: 1px;
    background: rgba(255, 255, 255, 0.08);
}

.modal-raw-formula {
    background: #04070a;
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 8px;
    padding: 1rem 1.25rem;
    font-family: var(--concept-mono);
    font-size: 0.9rem;
    color: #e2e8f0;
    position: relative;
    overflow-x: auto;
    min-width: 0;
    margin: 0.75rem 0;
}

.btn-copy-formula-btn {
    position: absolute;
    right: 0.75rem;
    top: 0.75rem;
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.12);
    color: var(--concept-text-sec);
    font-size: 0.72rem;
    font-family: var(--concept-mono);
    padding: 0.25rem 0.55rem;
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-copy-formula-btn:hover {
    color: #ffffff;
    border-color: rgba(255, 255, 255, 0.25);
    background: rgba(255, 255, 255, 0.12);
}

.modal-params-pre {
    background: rgba(12, 19, 25, 0.6);
    border: 1px solid rgba(255, 255, 255, 0.06);
    border-radius: 6px;
    padding: 1rem;
    font-family: var(--concept-mono);
    font-size: 0.8rem;
    line-height: 1.7;
    color: var(--concept-text-sec);
    white-space: pre-wrap;
    /* Long unbroken math tokens (e.g. ϕ(L)=1−ϕ_1L−…−ϕ_pL^p) must be
       allowed to break mid-token so they don't inflate the modal. */
    overflow-wrap: anywhere;
    margin: 0.75rem 0;
}

.modal-intuition-box {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-left: 3px solid rgba(45, 212, 191, 0.6);
    border-radius: 8px;
    padding: 1.25rem;
    margin: 1.5rem 0;
}

.modal-intuition-title {
    font-family: var(--concept-mono);
    font-size: 0.72rem;
    font-weight: 700;
    color: #2dd4bf;
    letter-spacing: 0.08em;
    margin-bottom: 0.5rem;
}

.modal-intuition-text {
    font-size: 0.92rem;
    color: #e2e8f0;
    font-style: italic;
    line-height: 1.65;
}

/* Action Primary Button (e.g. Scholar link) */
.btn-action-primary {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    background: rgba(255, 255, 255, 0.08);
    border: 1px solid rgba(255, 255, 255, 0.16);
    color: #ffffff;
    font-size: 0.82rem;
    font-family: var(--concept-mono);
    font-weight: 600;
    padding: 0.55rem 1rem;
    border-radius: 6px;
    text-decoration: none;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-action-primary:hover {
    background: rgba(255, 255, 255, 0.14);
    border-color: rgba(45, 212, 191, 0.4);
    color: #5eead4;
}

/* Pagination */
.concepts-page-nav {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.4rem;
    margin: 2rem 0 4rem;
}

.btn-page {
    background: rgba(15, 23, 31, 0.9);
    border: 1px solid var(--concept-border);
    border-radius: 6px;
    color: var(--concept-text-sec);
    font-size: 0.82rem;
    font-family: var(--concept-mono);
    padding: 0.4rem 0.75rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-page:hover:not(:disabled) {
    color: #ffffff;
    border-color: rgba(255, 255, 255, 0.25);
    background: rgba(255, 255, 255, 0.06);
}

.btn-page.active {
    background: rgba(255, 255, 255, 0.12);
    border-color: rgba(255, 255, 255, 0.28);
    color: #ffffff;
    font-weight: 700;
}

.btn-page:disabled {
    opacity: 0.35;
    cursor: not-allowed;
}

/* Toast */
.concepts-toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: #090e13;
    border: 1px solid rgba(255, 255, 255, 0.15);
    border-radius: 6px;
    color: #e2e8f0;
    font-family: var(--concept-mono);
    font-size: 0.8rem;
    padding: 0.65rem 1.15rem;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.6);
    z-index: 2000;
    opacity: 0;
    transform: translateY(15px);
    transition: all 0.25s ease;
    pointer-events: none;
}

.concepts-toast.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ==========================================================================
   Comprehensive Mobile & Tablet Responsive Engine - Concepts Library
   ========================================================================== */

@media (max-width: 860px) {
    .concepts-navbar {
        padding: 0 1.25rem;
    }

    .concepts-page-header {
        flex-direction: column;
        align-items: flex-start;
        padding: 1.6rem 1.25rem 0.85rem;
        gap: 1.1rem;
    }

    .concepts-header-stats {
        width: 100%;
        justify-content: space-around;
        padding: 0.65rem 1rem;
    }

    .concepts-section-tabs,
    .concepts-filter-bar,
    .concepts-meta-strip,
    .concepts-table-wrap,
    .concepts-cards-grid {
        padding: 0 1.25rem;
    }

    .concepts-cards-grid {
        grid-template-columns: 1fr;
    }

    .filter-dropdown {
        max-width: 100%;
        flex: 1;
    }
}

@media (max-width: 680px) {
    /* Navbar */
    .concepts-navbar {
        height: 58px;
        padding: 0 0.85rem;
    }

    .concepts-nav-brand img {
        height: 28px;
    }

    .concepts-badge-pill {
        font-size: 0.65rem;
        padding: 0.2rem 0.5rem;
    }

    .concepts-nav-right {
        gap: 0.4rem;
    }

    .nav-tv-btn {
        padding: 0.35rem 0.55rem;
        font-size: 0.74rem;
    }

    .tv-text-full {
        display: none !important;
    }

    .tv-text-short {
        display: inline !important;
    }

    .btn-nav-home {
        font-size: 0.76rem;
        padding: 0.35rem 0.6rem;
        background: rgba(255, 255, 255, 0.04);
        border: 1px solid var(--concept-border);
        border-radius: 6px;
        display: inline-flex;
        align-items: center;
    }

    .btn-home-text-full {
        display: none !important;
    }

    .btn-home-text-short {
        display: inline !important;
    }

    /* Page Header */
    .concepts-page-header {
        padding: 1.25rem 0.85rem 0.5rem;
        gap: 0.85rem;
    }

    .concepts-page-header h1 {
        font-size: clamp(1.4rem, 6vw, 2.2rem);
        margin-bottom: 0.35rem;
    }

    .concepts-page-header p {
        font-size: 0.84rem;
        line-height: 1.5;
    }

    .concepts-header-stats {
        padding: 0.55rem 0.75rem;
        border-radius: 10px;
    }

    .stat-item-num {
        font-size: 1.15rem;
    }

    .stat-item-lbl {
        font-size: 0.58rem;
    }

    /* Section Tabs: 2x2 Clean Mobile Grid */
    .concepts-section-tabs {
        padding: 0 0.85rem;
        margin: 1rem auto 0.75rem;
    }

    .section-tabs-bar {
        grid-template-columns: repeat(2, 1fr) !important;
        gap: 0.35rem;
        padding: 0.25rem;
        border-radius: 10px;
    }

    .btn-section-tab {
        font-size: 0.74rem;
        padding: 0.45rem 0.4rem;
        min-height: 38px;
        justify-content: space-between;
    }

    .tab-count-badge {
        font-size: 0.62rem;
        padding: 0.1rem 0.35rem;
    }

    /* Filter Bar */
    .concepts-filter-bar {
        padding: 0 0.85rem;
        margin-bottom: 1rem;
    }

    .filter-bar-inner {
        padding: 0.75rem;
        border-radius: 10px;
        gap: 0.55rem;
    }

    .filter-top-row {
        flex-direction: column;
        align-items: stretch;
        gap: 0.5rem;
    }

    .search-input-box {
        min-width: 0 !important;
        width: 100%;
    }

    .concept-search-field {
        height: 40px;
        font-size: 0.82rem;
        padding: 0 2.2rem;
        width: 100%;
        box-sizing: border-box;
    }

    .filter-dropdown {
        width: 100% !important;
        max-width: 100% !important;
        min-width: 0 !important;
        height: 38px;
        font-size: 0.8rem;
        box-sizing: border-box;
    }

    .filter-top-row .btn-page {
        width: 100%;
        height: 36px;
        justify-content: center;
        text-align: center;
        display: inline-flex;
        align-items: center;
    }

    .filter-tags-row {
        padding-bottom: 0.3rem;
        -webkit-overflow-scrolling: touch;
    }

    .filter-tag-pill {
        min-height: 32px;
        padding: 0.25rem 0.6rem;
        font-size: 0.7rem;
        display: inline-flex;
        align-items: center;
    }

    /* Meta Strip */
    .concepts-meta-strip {
        padding: 0 0.85rem;
        margin-bottom: 0.75rem;
        flex-direction: column;
        align-items: flex-start;
        gap: 0.45rem;
        font-size: 0.76rem;
    }

    .concepts-meta-strip .btn-page {
        width: 100%;
        text-align: center;
        min-height: 32px;
        display: inline-flex;
        align-items: center;
        justify-content: center;
    }

    /* Concepts Table */
    .concepts-table-wrap {
        padding: 0 0.85rem;
        margin-bottom: 2rem;
        border-radius: 10px;
        -webkit-overflow-scrolling: touch;
    }

    .concepts-flat-table {
        min-width: 460px;
        font-size: 0.78rem;
    }

    .concepts-flat-table th {
        padding: 0.65rem 0.6rem;
        font-size: 0.65rem;
    }

    .concepts-flat-table td {
        padding: 0.65rem 0.6rem;
        font-size: 0.78rem;
    }

    /* Concepts Cards */
    .concepts-cards-grid {
        padding: 0 0.85rem;
        grid-template-columns: 1fr;
        gap: 0.85rem;
        margin-bottom: 2rem;
    }

    .concept-item-card {
        padding: 1rem 0.85rem;
        border-radius: 10px;
    }

    .card-concept-title {
        font-size: 1.05rem;
    }

    .card-math-box {
        font-size: 0.72rem;
        padding: 0.5rem 0.65rem;
        overflow-x: auto;
    }

    .card-coord-vars {
        font-size: 0.75rem;
        padding: 0.45rem 0.65rem;
        overflow-x: auto;
    }

    /* Pagination */
    .concepts-page-nav {
        margin: 1.5rem 0 3rem;
        gap: 0.3rem;
        flex-wrap: wrap;
        justify-content: center;
    }

    .btn-page {
        padding: 0.4rem 0.6rem;
        min-height: 38px;
        min-width: 36px;
        font-size: 0.78rem;
        display: inline-flex;
        align-items: center;
        justify-content: center;
    }

    /* Modal Dossier */
    .concept-modal-backdrop {
        padding: 0.5rem;
    }

    .concept-modal-window {
        max-height: 94vh;
        max-height: 94svh;
        width: 100%;
        border-radius: 12px;
    }

    .concept-modal-header {
        padding: 0.75rem 0.85rem;
        flex-wrap: wrap;
        gap: 0.45rem;
    }

    .concept-modal-scroll {
        padding: 1rem 0.85rem 1.5rem;
        -webkit-overflow-scrolling: touch;
    }

    .concept-modal-scroll h2 {
        font-size: 1.25rem !important;
        line-height: 1.3 !important;
    }

    .modal-raw-formula {
        padding: 0.85rem;
        font-size: 0.8rem;
    }

    .modal-raw-formula pre {
        padding-top: 1.75rem;
    }

    .btn-copy-formula-btn {
        top: 0.4rem;
        right: 0.4rem;
        font-size: 0.68rem;
        padding: 0.2rem 0.45rem;
    }

    .modal-intuition-box {
        padding: 0.85rem;
        margin: 1rem 0;
    }

    .modal-params-pre {
        padding: 0.75rem;
        font-size: 0.74rem;
        overflow-x: auto;
    }
}

@media (max-width: 420px) {
    .concepts-navbar {
        height: 54px;
        padding: 0 0.65rem;
    }

    .concepts-nav-brand img {
        height: 26px;
    }

    .concepts-badge-pill {
        display: none !important;
    }

    .tv-announcement-badge {
        display: none !important;
    }

    .nav-tv-btn {
        padding: 0.35rem 0.5rem;
        min-width: 36px;
        justify-content: center;
    }

    .nav-ssrn-btn {
        padding: 0.35rem 0.5rem;
        font-size: 0.72rem;
    }

    .btn-nav-home {
        padding: 0.35rem 0.5rem;
        font-size: 0.72rem;
    }

    /* Bottom Sheet Style Modal on small phones */
    .concept-modal-backdrop {
        padding: 0;
        align-items: flex-end;
    }

    .concept-modal-window {
        max-height: 96vh;
        max-height: 96svh;
        border-bottom-left-radius: 0;
        border-bottom-right-radius: 0;
        border-radius: 16px 16px 0 0;
    }

    /* Bigger close-button tap target on phones */
    .btn-close-modal {
        min-width: 36px;
        min-height: 36px;
        font-size: 1.4rem;
    }
}

/* iOS Safe Area Inset Support */
@supports (padding-top: env(safe-area-inset-top)) {
    .concepts-navbar {
        padding-left: max(0.85rem, env(safe-area-inset-left));
        padding-right: max(0.85rem, env(safe-area-inset-right));
    }

    .concepts-page-header,
    .concepts-section-tabs,
    .concepts-filter-bar,
    .concepts-meta-strip,
    .concepts-table-wrap,
    .concepts-cards-grid {
        padding-left: max(0.85rem, env(safe-area-inset-left));
        padding-right: max(0.85rem, env(safe-area-inset-right));
    }
}

/* ==========================================================================
   Mobile Performance & Touch Optimization Layer
   ========================================================================== */

.concepts-page-body {
    min-height: 100dvh;
    -webkit-tap-highlight-color: transparent;
}

button, a, select, input, .filter-tag-pill, .btn-section-tab {
    touch-action: manipulation;
}

@media (max-width: 860px) {
    /* backdrop-filter blur is GPU-expensive on low-end phones — halve it */
    .concepts-navbar,
    .filter-bar-inner,
    .concept-card,
    .concepts-table-wrap {
        backdrop-filter: blur(8px);
        -webkit-backdrop-filter: blur(8px);
    }

    /* Prevent iOS Safari auto-zoom on input focus (needs >= 16px) */
    .concept-search-field,
    .filter-dropdown {
        font-size: 16px;
    }

    /* Comfortable tap targets for tag pills */
    .filter-tag-pill {
        min-height: 36px;
    }
}

/* Reduced motion: honor OS accessibility setting */
@media (prefers-reduced-motion: reduce) {
    html {
        scroll-behavior: auto;
    }

    #particles {
        display: none;
    }

    .concepts-loading-spinner {
        animation: none;
        border-top-color: var(--concept-border);
    }

    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}