/* ==========================================================================
   GraphLab 3D — Precision Mathematical Split-Pane Drafting Stylesheet
   Aesthetic: Desmos / Linear / Millimeter Coordinate Porcelain & Cobalt Ink
   Strict Zero-Drift Grid & Arabic RTL BiDi Isolation Rules Enforced
   ========================================================================== */

:root {
  --bg-page: #F8FAFC;
  --bg-panel: #FFFFFF;
  --bg-subtle: #F1F5F9;
  --bg-code: #0F172A;
  --ink-primary: #0F172A;
  --ink-secondary: #334155;
  --ink-muted: #64748B;
  --border-light: #E2E8F0;
  --border-strong: #CBD5E1;

  --cobalt: #1D4ED8;
  --cobalt-soft: #EFF6FF;
  --cobalt-border: #BFDBFE;
  --vermilion: #DC2626;
  --vermilion-soft: #FEF2F2;
  --emerald: #047857;
  --emerald-soft: #ECFDF5;
  --amber: #B45309;
  --amber-soft: #FFFBEB;

  --font-sans: 'Plus Jakarta Sans', 'IBM Plex Sans Arabic', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'IBM Plex Sans Arabic', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --radius-sm: 4px;
  --radius-md: 6px;
  --shadow-subtle: 0 1px 2px rgba(15, 23, 42, 0.04);
}

*, *::before, *::after {
  box-sizing: border-box;
}

/* CRITICAL RTL TYPOGRAPHY RULE: Never apply letter-spacing to Arabic script */
html[dir="rtl"],
html[dir="rtl"] * {
  letter-spacing: 0 !important;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg-page);
  color: var(--ink-primary);
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a {
  color: var(--cobalt);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

/* Strict BiDi Isolation for all mathematical expressions, numbers, units & matrices */
.math-ltr,
.math-input,
.matrix-cell-input,
.kv-math,
.formula-chip,
.coord-pill {
  direction: ltr !important;
  unicode-bidi: isolate !important;
  font-family: var(--font-mono);
}

bdi[dir="ltr"] {
  display: inline-block;
  direction: ltr !important;
  unicode-bidi: isolate-override !important;
  font-family: var(--font-mono);
}

html[dir="rtl"] .kv-math,
html[dir="rtl"] .math-input {
  text-align: left;
}

/* --- Top Navigation Header --- */
.top-header {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-strong);
}

.header-inner {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 18px;
  min-height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  flex-wrap: wrap;
}

.brand-link {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--ink-primary);
  font-weight: 700;
  font-size: 1.05rem;
  text-decoration: none !important;
}

.brand-mark {
  width: 30px;
  height: 30px;
  border-radius: var(--radius-sm);
  background: var(--cobalt);
  color: #FFFFFF;
  display: inline-grid;
  place-items: center;
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.88rem;
  flex-shrink: 0;
}

.brand-sub {
  font-size: 0.76rem;
  color: var(--ink-muted);
  font-weight: 500;
  display: none;
}
@media (min-width: 1120px) {
  .brand-sub {
    display: inline;
    padding-inline-start: 8px;
    border-inline-start: 1px solid var(--border-strong);
  }
}

.nav-tabs {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}

.nav-tab {
  padding: 7px 11px;
  border-radius: var(--radius-sm);
  color: var(--ink-secondary);
  font-size: 0.87rem;
  font-weight: 600;
  border: 1px solid transparent;
  transition: background 0.12s ease, color 0.12s ease, border-color 0.12s ease;
  text-decoration: none !important;
}

.nav-tab:hover {
  background: var(--bg-subtle);
  color: var(--ink-primary);
}

.nav-tab.active {
  background: var(--cobalt-soft);
  color: var(--cobalt);
  border-color: var(--cobalt-border);
}

.lang-switch {
  padding: 5px 11px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: var(--bg-panel);
  color: var(--ink-primary);
  font-size: 0.82rem;
  font-weight: 600;
  text-decoration: none !important;
}
.lang-switch:hover {
  background: var(--bg-subtle);
}

/* --- Main Container & Compact Breadcrumb Context Bar --- */
.page-shell {
  max-width: 1400px;
  margin: 0 auto;
  padding: 14px 18px 48px;
}

.context-strip {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  padding-bottom: 12px;
  margin-bottom: 14px;
  border-bottom: 1px solid var(--border-light);
}

.context-title {
  margin: 0;
  font-size: 1.24rem;
  font-weight: 700;
  color: var(--ink-primary);
  line-height: 1.35;
}

.context-summary {
  margin: 4px 0 0;
  font-size: 0.9rem;
  color: var(--ink-secondary);
  max-width: 920px;
}

.breadcrumb-trail {
  font-size: 0.8rem;
  color: var(--ink-muted);
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

/* --- Split-Pane Mathematical Studio Grid (ZERO-DRIFT LOCKED) --- */
.studio-grid {
  display: grid;
  grid-template-columns: 380px minmax(0, 1fr);
  gap: 16px;
  align-items: start;
}

@media (max-width: 980px) {
  .studio-grid {
    grid-template-columns: minmax(0, 1fr);
  }
}

.studio-sidebar,
.studio-stage,
.panel-card,
.surface-dual-grid > * {
  min-width: 0;
  max-width: 100%;
}

.panel-card {
  background: var(--bg-panel);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-subtle);
  overflow: hidden;
}

.panel-head {
  padding: 10px 14px;
  background: var(--bg-subtle);
  border-bottom: 1px solid var(--border-light);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  flex-wrap: wrap;
}

.panel-title {
  margin: 0;
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--ink-primary);
}

.viewport-frame,
.slider-row,
.panel-head,
.seg-bar {
  user-select: none;
  -webkit-user-select: none;
}

bdi[dir="ltr"] {
  display: inline-block;
  direction: ltr !important;
  unicode-bidi: isolate !important;
  font-family: var(--font-mono);
  font-size: 0.92em;
}

.panel-body {
  padding: 14px;
}

/* --- Expression Rows & Form Controls --- */
.control-group {
  margin-bottom: 12px;
}
.control-group:last-child {
  margin-bottom: 0;
}

.control-label {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 6px;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--ink-secondary);
  margin-bottom: 5px;
}

.trace-dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 2px;
  margin-inline-end: 6px;
}

.math-input,
.select-input,
.num-input {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: #FFFFFF;
  color: var(--ink-primary);
  font-size: 0.9rem;
  transition: border-color 0.12s ease, box-shadow 0.12s ease;
}

.math-input:focus,
.select-input:focus,
.num-input:focus,
.matrix-cell-input:focus {
  outline: none;
  border-color: var(--cobalt);
  box-shadow: 0 0 0 2px rgba(29, 78, 216, 0.14);
}

.inline-row-2 {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
}

.inline-row-3 {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 8px;
}

.inline-row-4 {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 6px;
}

.slider-row {
  padding: 7px 9px;
  background: var(--bg-page);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  margin-bottom: 8px;
}

.slider-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.8rem;
  margin-bottom: 3px;
}

input[type="range"] {
  width: 100%;
  accent-color: var(--cobalt);
  cursor: pointer;
  margin: 0;
  display: block;
}

/* Segmented Mode Switcher */
.seg-bar {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(72px, 1fr));
  gap: 4px;
  background: var(--bg-subtle);
  padding: 3px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-light);
  margin-bottom: 12px;
}

.seg-btn {
  padding: 6px 8px;
  border: none;
  border-radius: 3px;
  background: transparent;
  color: var(--ink-secondary);
  font-family: inherit;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
}

.seg-btn.active {
  background: #FFFFFF;
  color: var(--cobalt);
  box-shadow: 0 1px 2px rgba(15, 23, 42, 0.08);
}

.btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.btn {
  padding: 7px 12px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong);
  background: #FFFFFF;
  color: var(--ink-primary);
  font-family: inherit;
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.12s ease, border-color 0.12s ease;
}
.btn:hover {
  background: var(--bg-subtle);
}

.btn-primary {
  background: var(--cobalt);
  border-color: var(--cobalt);
  color: #FFFFFF;
}
.btn-primary:hover {
  background: #1E40AF;
}

.status-banner {
  padding: 8px 10px;
  border-radius: var(--radius-sm);
  font-size: 0.82rem;
  margin-top: 8px;
  display: none;
}
.status-banner.error {
  display: block;
  background: var(--vermilion-soft);
  border: 1px solid #FECACA;
  color: #991B1B;
}
.status-banner.ok {
  display: block;
  background: var(--emerald-soft);
  border: 1px solid #A7F3D0;
  color: #065F46;
}

/* --- Canvas Viewport Frame (FIXED CSS DIMENSIONS -> ZERO FEEDBACK DRIFT) --- */
.viewport-frame {
  position: relative;
  width: 100%;
  height: 460px;
  min-width: 0;
  background-color: #FFFFFF;
  border-bottom: 1px solid var(--border-light);
  overflow: hidden;
  touch-action: none;
}

.viewport-frame.compact {
  height: 360px;
}

.viewport-frame canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.viewport-hud {
  position: absolute;
  top: 10px;
  inset-inline-end: 10px;
  display: flex;
  align-items: center;
  gap: 5px;
  z-index: 4;
}

.hud-btn {
  padding: 4px 9px;
  font-size: 0.78rem;
  font-weight: 600;
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  color: var(--ink-primary);
  cursor: pointer;
}
.hud-btn:hover {
  background: var(--bg-subtle);
}

.coord-readout {
  position: absolute;
  bottom: 10px;
  left: 10px;
  padding: 4px 9px;
  font-size: 0.78rem;
  background: rgba(15, 23, 42, 0.86);
  color: #F8FAFC;
  border-radius: var(--radius-sm);
  pointer-events: none;
}

/* Dual 3D Mesh + 2D Contour Stage */
.surface-dual-grid {
  display: grid;
  grid-template-columns: 1.35fr 1fr;
  gap: 12px;
  padding: 12px;
}
@media (max-width: 1100px) {
  .surface-dual-grid {
    grid-template-columns: minmax(0, 1fr);
  }
}

.sub-viewport-card {
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: #FFFFFF;
}

.sub-viewport-label {
  padding: 6px 10px;
  font-size: 0.78rem;
  font-weight: 700;
  background: var(--bg-subtle);
  border-bottom: 1px solid var(--border-light);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* --- Key-Value Readout Tables & Feature Pins --- */
.kv-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 8px;
}

.kv-item {
  padding: 8px 11px;
  background: var(--bg-page);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  display: flex;
  flex-direction: column;
  gap: 3px;
  min-width: 0;
}

.kv-label {
  font-size: 0.76rem;
  color: var(--ink-muted);
  font-weight: 600;
}

.kv-math {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--ink-primary);
  overflow-wrap: anywhere;
}

.kv-prose {
  font-size: 0.86rem;
  font-weight: 600;
  color: var(--ink-primary);
}

/* --- Matrix Editor & Authentic Bracket Display --- */
.matrix-editor-wrap {
  direction: ltr !important;
  unicode-bidi: isolate !important;
  overflow-x: auto;
  padding: 6px 0;
}

.matrix-bracket-box {
  display: inline-block;
  position: relative;
  padding: 6px 10px;
  border-left: 2px solid var(--ink-primary);
  border-right: 2px solid var(--ink-primary);
  direction: ltr !important;
}

.matrix-bracket-box::before,
.matrix-bracket-box::after {
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  width: 6px;
  border-top: 2px solid var(--ink-primary);
  border-bottom: 2px solid var(--ink-primary);
}
.matrix-bracket-box::before { left: 0; }
.matrix-bracket-box::after { right: 0; }

.matrix-input-grid {
  display: grid;
  gap: 5px;
}

.matrix-cell-input {
  width: 64px;
  padding: 6px;
  text-align: center;
  border: 1px solid var(--border-strong);
  border-radius: 3px;
  font-size: 0.86rem;
  background: #FFFFFF;
}

.matrix-aug-sep {
  border-left: 2px dashed var(--cobalt) !important;
  padding-left: 8px;
}

/* Step-by-Step Ledger Cards */
.step-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 12px;
}

.step-card {
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  background: var(--bg-page);
  padding: 10px 12px;
}

.step-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 8px;
}

.step-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--cobalt);
  background: var(--cobalt-soft);
  border: 1px solid var(--cobalt-border);
  padding: 2px 8px;
  border-radius: 3px;
}

.matrix-table {
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: 0.84rem;
}

.matrix-table td {
  padding: 4px 10px;
  text-align: right;
  white-space: nowrap;
}

.matrix-table td.aug-col {
  border-left: 1.5px dashed var(--cobalt);
  color: var(--cobalt);
  font-weight: 700;
}

/* Data Tables (Quadrature, Taylor, Harmonics, ODE RK4) */
.data-table-wrap {
  overflow-x: auto;
  margin-top: 10px;
}

.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.84rem;
}

.data-table th,
.data-table td {
  padding: 7px 10px;
  border-bottom: 1px solid var(--border-light);
  text-align: start;
}

.data-table th {
  background: var(--bg-subtle);
  font-weight: 700;
  color: var(--ink-secondary);
  font-size: 0.78rem;
}

/* --- Below-the-Fold Preset Cards, Worked Reference & FAQ --- */
.section-block {
  margin-top: 28px;
}

.section-heading {
  font-size: 1.08rem;
  font-weight: 700;
  margin: 0 0 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-strong);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.preset-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(275px, 1fr));
  gap: 12px;
}

.preset-card {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 8px;
  padding: 13px 14px;
  background: var(--bg-panel);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius-md);
  color: var(--ink-primary);
  text-decoration: none !important;
  transition: border-color 0.14s ease, transform 0.14s ease;
}

.preset-card:hover {
  border-color: var(--cobalt);
  transform: translateY(-1px);
}

.preset-cat {
  font-size: 0.73rem;
  font-weight: 700;
  color: var(--cobalt);
  text-transform: uppercase;
}

.preset-name {
  font-size: 0.93rem;
  font-weight: 700;
  line-height: 1.38;
  margin: 2px 0;
}

.preset-desc {
  font-size: 0.82rem;
  color: var(--ink-secondary);
  margin: 0;
}

.formula-chip {
  display: inline-block;
  padding: 3px 7px;
  background: var(--bg-subtle);
  border: 1px solid var(--border-light);
  border-radius: 3px;
  font-size: 0.79rem;
  color: var(--ink-primary);
  max-width: 100%;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.doc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 14px;
}

.doc-card {
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-md);
  padding: 16px;
}

.doc-card h3 {
  margin: 0 0 8px;
  font-size: 0.96rem;
}

.doc-card p {
  margin: 0;
  font-size: 0.87rem;
  color: var(--ink-secondary);
}

.faq-list {
  display: grid;
  gap: 8px;
}

.faq-item {
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-sm);
  padding: 11px 14px;
}

.faq-item summary {
  font-weight: 700;
  font-size: 0.9rem;
  cursor: pointer;
}

.faq-item p {
  margin: 8px 0 0;
  font-size: 0.86rem;
  color: var(--ink-secondary);
}

.site-footer {
  margin-top: 44px;
  padding: 22px 18px;
  border-top: 1px solid var(--border-strong);
  background: var(--bg-panel);
  font-size: 0.82rem;
  color: var(--ink-muted);
}

.footer-inner {
  max-width: 1400px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}