:root {
  color-scheme: light;
  --ink: #1d2633;
  --muted: #667085;
  --line: #d9e0e8;
  --paper: #fbfcfe;
  --panel: #ffffff;
  --teal: #0f766e;
  --red: #c2410c;
  --violet: #6d28d9;
  --amber: #b7791f;
  --blue: #2563eb;
  --shadow: 0 18px 45px rgba(20, 30, 45, 0.12);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 18px;
  background:
    linear-gradient(90deg, rgba(37, 99, 235, 0.08) 1px, transparent 1px),
    linear-gradient(0deg, rgba(15, 118, 110, 0.08) 1px, transparent 1px),
    #eef3f7;
  background-size: 42px 42px;
}

button,
input,
select {
  font: inherit;
}

.app-shell {
  width: min(1760px, 100%);
  height: 100dvh;
  min-height: 100dvh;
  margin: 0 auto;
  padding: 24px;
  overflow: hidden;
}

.hub-shell {
  width: min(1180px, 100%);
  min-height: 100vh;
  margin: 0 auto;
  padding: 32px 24px;
}

.hub-hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, 520px);
  gap: 24px;
  align-items: end;
  padding: 32px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.92);
  box-shadow: var(--shadow);
}

.hub-lead {
  margin: 0;
  color: var(--muted);
  font-size: 1.25rem;
  font-weight: 750;
  line-height: 1.6;
}

.animation-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 18px;
  margin-top: 22px;
}

.animation-card {
  display: grid;
  gap: 10px;
  min-height: 220px;
  padding: 22px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  text-decoration: none;
  box-shadow: var(--shadow);
  transition: transform 160ms ease, border-color 160ms ease;
}

.animation-card:hover {
  transform: translateY(-3px);
  border-color: rgba(15, 118, 110, 0.55);
}

.animation-card strong {
  font-size: 1.55rem;
  line-height: 1.2;
}

.animation-card span:last-child {
  color: var(--muted);
  font-size: 1.08rem;
  font-weight: 700;
  line-height: 1.55;
}

.card-kicker {
  color: var(--teal);
  font-size: 0.92rem;
  font-weight: 900;
}

.placeholder-card {
  opacity: 0.72;
}

.workspace {
  height: calc(100dvh - 48px);
  min-height: 0;
  display: grid;
  grid-template-rows: auto auto auto auto minmax(0, 1fr);
  gap: 18px;
}

.workspace.has-division-detail {
  grid-template-rows: auto auto auto auto auto minmax(0, 1fr);
}

.workspace.has-equation-band {
  grid-template-rows: auto auto auto auto auto minmax(0, 1fr);
}

.workspace.has-inverse-display {
  grid-template-rows: auto auto auto auto auto auto minmax(0, 1fr);
}

.workspace > * {
  min-height: 0;
}

.topbar {
  grid-row: 1;
}

.control-band {
  grid-row: 2;
}

.message {
  grid-row: 3;
}

.matrix-stage {
  grid-row: 4;
}

.equation-display-band {
  grid-row: 4;
}

.inverse-display-band {
  grid-row: 4;
}

.workspace.has-equation-band .matrix-stage {
  grid-row: 5;
}

.workspace.has-inverse-display .matrix-stage {
  grid-row: 5;
}

.verification-band {
  grid-row: 6;
}

.division-detail {
  grid-row: 5;
}

.animation-band {
  grid-row: 5;
}

.workspace.has-equation-band .animation-band {
  grid-row: 6;
}

.workspace.has-inverse-display .animation-band {
  grid-row: 7;
}

.workspace.has-division-detail .animation-band {
  grid-row: 6;
}

.topbar,
.control-band,
.animation-band,
.equation-display-band,
.inverse-display-band,
.verification-band {
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 20px;
  border-radius: 8px;
}

.eyebrow {
  margin: 0 0 4px;
  color: var(--teal);
  font-size: 0.9rem;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

h1,
h2 {
  margin: 0;
  letter-spacing: 0;
}

h1 {
  font-size: clamp(2rem, 3.4vw, 3.6rem);
  line-height: 1.05;
}

h2 {
  font-size: 1.35rem;
}

.status-strip {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: flex-end;
}

.status-strip span {
  min-width: 86px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--paper);
  color: var(--muted);
  text-align: center;
  font-weight: 700;
  font-size: 1.05rem;
}

.home-link {
  display: inline-grid;
  min-width: 86px;
  min-height: 40px;
  place-items: center;
  padding: 8px 12px;
  border: 1px solid rgba(15, 118, 110, 0.42);
  border-radius: 999px;
  background: rgba(15, 118, 110, 0.09);
  color: var(--teal);
  text-align: center;
  text-decoration: none;
  font-size: 1.05rem;
  font-weight: 800;
}

.control-band {
  display: grid;
  grid-template-columns: minmax(180px, 240px) minmax(340px, 1fr) minmax(260px, auto);
  gap: 16px;
  align-items: end;
  padding: 18px;
  border-radius: 8px;
}

.method-controls {
  grid-template-columns: minmax(180px, 240px) minmax(260px, auto);
  justify-content: start;
}

.control-group {
  display: grid;
  gap: 8px;
}

.control-group > label {
  color: var(--muted);
  font-size: 1rem;
  font-weight: 800;
}

select,
input[type="number"] {
  height: 48px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: #fff;
  color: var(--ink);
  padding: 0 10px;
}

select,
input[type="number"],
input[type="text"] {
  font-size: 1.05rem;
}

.size-grid {
  display: grid;
  grid-template-columns: auto 72px auto 72px auto 72px auto 72px;
  gap: 8px;
  align-items: center;
}

.size-grid span {
  color: var(--muted);
  font-weight: 800;
  text-align: center;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

button {
  min-height: 48px;
  border: 0;
  border-radius: 6px;
  padding: 0 14px;
  cursor: pointer;
  font-weight: 800;
  font-size: 1.05rem;
}

.primary {
  background: var(--teal);
  color: #fff;
}

.secondary {
  background: #e7eef7;
  color: var(--ink);
}

button:focus-visible,
input:focus-visible,
select:focus-visible {
  outline: 3px solid rgba(37, 99, 235, 0.28);
  outline-offset: 2px;
}

.message {
  min-height: 24px;
  color: var(--red);
  font-weight: 800;
  font-size: 1.08rem;
}

.message:empty {
  visibility: hidden;
}

.matrix-stage {
  display: grid;
  grid-template-columns: minmax(240px, 1fr) auto minmax(240px, 1fr) auto minmax(240px, 1fr);
  gap: 14px;
  align-items: center;
  align-self: start;
}

.method-stage {
  grid-template-columns: minmax(260px, 0.45fr) minmax(720px, 1.55fr);
}

.matrix-panel {
  min-width: 0;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
  padding: 16px;
}

.method-wide {
  border-color: rgba(37, 99, 235, 0.34);
}

.equation-display-band {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 10px;
  align-items: start;
  padding: 14px 16px;
  border-radius: 8px;
  overflow: auto;
}

.inverse-display-band {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 16px;
  align-items: center;
  padding: 14px 16px;
  border-radius: 8px;
  overflow: auto;
}

.verification-band {
  display: grid;
  gap: 10px;
  padding: 14px 16px;
  border-radius: 8px;
  overflow: hidden;
}

.equation-display-header {
  display: grid;
  gap: 4px;
}

.inverse-display-header,
.verification-header {
  display: grid;
  gap: 4px;
}

.equation-display-header h2,
.inverse-display-header h2,
.verification-header h2 {
  font-size: 1.28rem;
}

.equation-display-header span,
.inverse-display-header span,
.verification-header span {
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 800;
}

.verification-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr) auto minmax(0, 1fr);
  gap: 12px;
  align-items: center;
  min-width: 0;
  overflow: hidden;
  padding-bottom: 4px;
}

.verification-panel {
  min-width: 0;
  padding: 12px;
}

.verification-panel header {
  margin-bottom: 8px;
}

.verify-matrix {
  --matrix-cell-min: 0px;
  gap: 6px;
  padding: 8px;
  overflow: hidden;
}

.verify-matrix .cell-output {
  min-width: 0;
  min-height: 38px;
  font-size: clamp(0.76rem, 0.9vw, 1.08rem);
  padding: 0 6px;
}

.inverse-equation {
  display: flex;
  align-items: center;
  gap: 18px;
  min-width: 0;
  overflow-x: auto;
}

.math-matrix-term {
  display: grid;
  gap: 6px;
  justify-items: center;
  flex: 0 0 auto;
}

.math-matrix-label {
  color: var(--muted);
  font-size: 1rem;
  font-weight: 900;
}

.math-matrix-label sup {
  font-size: 0.7em;
  line-height: 0;
  vertical-align: super;
}

.math-matrix {
  position: relative;
  display: grid;
  gap: 8px 12px;
  padding: 10px 18px;
  color: var(--ink);
  font-size: 1.34rem;
  font-weight: 900;
  line-height: 1.1;
}

.math-matrix::before,
.math-matrix::after {
  position: absolute;
  top: 4px;
  bottom: 4px;
  width: 10px;
  content: "";
  border-color: var(--ink);
}

.math-matrix::before {
  left: 0;
  border-top: 3px solid;
  border-bottom: 3px solid;
  border-left: 3px solid;
}

.math-matrix::after {
  right: 0;
  border-top: 3px solid;
  border-right: 3px solid;
  border-bottom: 3px solid;
}

.math-matrix-cell {
  min-width: 44px;
  text-align: center;
  white-space: nowrap;
}

.pending-math-matrix {
  color: var(--muted);
}

.math-equals {
  color: var(--ink);
  font-size: 1.6rem;
  font-weight: 900;
}

.equation-compare {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 10px;
  min-width: 0;
}

.equation-group {
  display: grid;
  gap: 8px;
  min-width: 0;
}

.equation-group-title {
  color: var(--muted);
  font-size: 0.96rem;
  font-weight: 900;
}

.equation-system {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 6px;
  min-width: 0;
  overflow: auto;
}

.equation-line {
  min-height: 46px;
  align-items: center;
  column-gap: 10px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
  color: var(--ink);
  font-size: 1.26rem;
  font-weight: 900;
  line-height: 1.25;
  overflow-wrap: anywhere;
}

.aligned-equation {
  display: grid;
}

.natural-equation {
  display: flex;
  flex-wrap: wrap;
  gap: 0 8px;
}

.equation-line sub,
.solution-cell sub {
  font-size: 0.68em;
  line-height: 0;
  vertical-align: sub;
}

.equation-term-text {
  white-space: nowrap;
}

.positive-term {
  padding-left: 0.08em;
}

.equation-sign,
.equation-equals {
  min-width: 20px;
  text-align: center;
}

.equation-equals {
  font-weight: 900;
}

.zero-term {
  visibility: hidden;
}

.equation-line.active-equation {
  border-color: rgba(183, 121, 31, 0.78);
  background: rgba(183, 121, 31, 0.18);
  color: #7c4a03;
}

.matrix-panel header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  margin-bottom: 14px;
}

.matrix-panel header span {
  color: var(--muted);
  font-weight: 800;
}

.matrix-input,
.matrix-output {
  display: grid;
  gap: 8px;
  align-content: stretch;
  min-height: auto;
  padding: 12px;
  border-left: 5px solid var(--ink);
  border-right: 5px solid var(--ink);
}

.matrix-output {
  --matrix-cell-min: 92px;
  overflow-x: auto;
}

.method-matrix {
  --matrix-cell-min: 112px;
  overflow: auto;
}

.cell-input,
.cell-output,
.flow-cell {
  width: 100%;
  aspect-ratio: 1 / 0.72;
  min-height: 46px;
  border-radius: 6px;
  display: grid;
  place-items: center;
  font-weight: 800;
  letter-spacing: 0;
  font-size: 1.22rem;
  line-height: 1.08;
  overflow-wrap: normal;
  white-space: nowrap;
  word-break: keep-all;
  text-align: center;
}

.cell-input {
  border: 1px solid #c8d3df;
  text-align: center;
  color: var(--ink);
  background: #f8fafc;
}

.matrix-input .cell-input,
.matrix-output .cell-output {
  min-height: 64px;
  font-size: clamp(1.05rem, 1.85vw, 1.75rem);
}

.matrix-input .cell-input {
  padding: 0 8px;
}

.cell-input.invalid {
  border-color: var(--red);
  background: rgba(194, 65, 12, 0.08);
}

.divider-left {
  border-left-width: 5px !important;
  border-left-color: var(--ink) !important;
}

.cell-input.referenced-a,
.cell-output.referenced-a {
  border-color: rgba(37, 99, 235, 0.82);
  background: rgba(37, 99, 235, 0.16);
  color: #1748b3;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.16);
}

.cell-input.referenced-b,
.cell-output.referenced-b {
  border-color: rgba(109, 40, 217, 0.82);
  background: rgba(109, 40, 217, 0.15);
  color: #5420ad;
  box-shadow: 0 0 0 3px rgba(109, 40, 217, 0.14);
}

.cell-output {
  border: 1px solid rgba(15, 118, 110, 0.25);
  color: var(--teal);
  background: rgba(15, 118, 110, 0.08);
  transition: transform 180ms ease, background 180ms ease;
}

.cell-output.active {
  transform: scale(1.06);
  background: rgba(183, 121, 31, 0.18);
  color: #7c4a03;
}

.method-cell {
  min-width: 112px;
  padding: 0 10px;
}

.method-cell.row-cell {
  background: rgba(37, 99, 235, 0.12);
  color: #1748b3;
}

.method-cell.pivot-cell {
  background: rgba(183, 121, 31, 0.22);
  border-color: rgba(183, 121, 31, 0.78);
  color: #7c4a03;
  transform: scale(1.04);
}

.solution-output {
  --matrix-cell-min: 180px;
  align-content: start;
}

.solution-cell {
  aspect-ratio: auto;
  display: inline-flex;
  align-items: baseline;
  justify-content: start;
  gap: 2px;
  padding: 0 14px;
  min-width: 180px;
}

.pending-solution {
  color: var(--muted);
  background: var(--paper);
  border-color: var(--line);
}

.operator-glyph {
  width: 58px;
  height: 58px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--ink);
  color: #fff;
  font-size: 1.75rem;
  font-weight: 900;
}

.operator-glyph.equals {
  background: var(--blue);
}

.result-panel {
  border-color: rgba(15, 118, 110, 0.42);
}

.division-detail {
  display: grid;
  gap: 12px;
  min-height: 0;
  padding: 14px 16px;
  border: 1px solid rgba(37, 99, 235, 0.28);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.86);
  box-shadow: 0 12px 28px rgba(20, 30, 45, 0.08);
  overflow-x: auto;
}

.division-detail[hidden] {
  display: none;
}

.division-note {
  color: var(--muted);
  font-size: 0.98rem;
  font-weight: 800;
  line-height: 1.45;
}

.inverse-proof-slot:empty {
  display: none;
}

.equation-row {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: max-content;
}

.inverse-proof {
  padding-bottom: 12px;
  border-bottom: 1px solid var(--line);
}

.equation-term {
  display: grid;
  gap: 6px;
  min-width: 96px;
}

.equation-label {
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 900;
  text-align: center;
}

.equation-label sup {
  font-size: 0.7em;
  line-height: 0;
  vertical-align: super;
}

.equation-operator {
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--ink);
  color: #fff;
  font-size: 1.28rem;
  font-weight: 900;
  flex: 0 0 auto;
}

.equation-button {
  border: 0;
  padding: 0;
  background: transparent;
  color: inherit;
  cursor: pointer;
}

.equation-link {
  color: inherit;
  text-decoration: none;
  cursor: pointer;
}

.clickable-term .mini-matrix {
  border-color: var(--violet);
  box-shadow: 0 0 0 3px rgba(109, 40, 217, 0.12);
}

.equation-button:hover .mini-matrix,
.equation-button:focus-visible .mini-matrix,
.equation-link:hover .mini-matrix,
.equation-link:focus-visible .mini-matrix {
  background: rgba(109, 40, 217, 0.08);
}

.mini-matrix {
  gap: 6px;
  padding: 8px;
  min-width: 84px;
  background: #fff;
}

.mini-matrix .cell-output {
  min-height: 38px;
  font-size: 1rem;
  line-height: 1;
}

.animation-band {
  display: grid;
  grid-template-columns: minmax(280px, 1fr) minmax(280px, 520px);
  grid-template-rows: minmax(0, 1fr);
  gap: 16px;
  padding: 16px;
  border-radius: 8px;
  align-self: stretch;
  align-items: stretch;
  height: 100%;
  min-height: 0;
  overflow: hidden;
}

.animation-band > *,
.formula-box > * {
  min-height: 0;
}

.timeline {
  height: 100%;
  min-height: 0;
  overflow-x: auto;
  overflow-y: hidden;
  padding: 10px;
  border: 1px dashed #c1ccd8;
  border-radius: 8px;
  background: var(--paper);
  display: flex;
  align-items: flex-start;
}

.animation-track {
  display: flex;
  align-items: center;
  gap: 10px;
  height: auto;
  min-height: 108px;
}

.flow-cell {
  width: auto;
  min-width: 220px;
  flex: 0 0 max-content;
  background: #fff;
  border: 1px solid var(--line);
  color: var(--muted);
  aspect-ratio: auto;
  padding: 0 16px;
  white-space: nowrap;
  overflow-wrap: normal;
}

.flow-cell.source-a {
  border-color: rgba(37, 99, 235, 0.35);
  color: var(--blue);
}

.flow-cell.source-b {
  border-color: rgba(109, 40, 217, 0.35);
  color: var(--violet);
}

.flow-cell.operator {
  min-width: 54px;
  flex-basis: 54px;
  padding: 0;
  background: var(--ink);
  color: #fff;
}

.flow-cell.result {
  min-width: 320px;
}

.flow-cell.result {
  border-color: rgba(15, 118, 110, 0.4);
  color: var(--teal);
  background: rgba(15, 118, 110, 0.08);
}

.flow-cell.pulse {
  animation: pulse 520ms ease;
}

.formula-box {
  min-height: 0;
  height: 100%;
  max-height: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  padding: 14px;
  display: grid;
  grid-template-rows: auto auto auto minmax(0, 1fr);
  overflow: hidden;
}

.formula-title {
  color: var(--muted);
  font-weight: 900;
  margin-bottom: 8px;
  font-size: 1.1rem;
}

.formula {
  line-height: 1.6;
  font-weight: 750;
  font-size: 1.2rem;
}

.history-title {
  margin-top: 16px;
  padding-top: 12px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-weight: 900;
  font-size: 1.05rem;
}

.history-list {
  display: block;
  height: auto;
  min-height: 0;
  max-height: none;
  margin: 10px 0 0;
  padding-left: 28px;
  padding-bottom: 8px;
  overflow-y: auto;
  overflow-x: hidden;
  overscroll-behavior: contain;
}

.history-list:empty {
  min-height: 0;
}

.history-list li {
  padding: 8px 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: var(--paper);
}

.history-list li + li {
  margin-top: 8px;
}

.history-list strong {
  display: block;
  margin-bottom: 4px;
  color: var(--teal);
}

.history-list span {
  overflow-wrap: anywhere;
}

@keyframes pulse {
  0% {
    transform: translateY(6px) scale(0.94);
    opacity: 0.35;
  }
  100% {
    transform: translateY(0) scale(1);
    opacity: 1;
  }
}

@media (max-width: 980px) {
  .app-shell {
    height: 100dvh;
    overflow: hidden;
  }

  .workspace {
    height: calc(100dvh - 48px);
    min-height: 0;
  }

  .hub-hero,
  .control-band,
  .equation-display-band,
  .equation-compare,
  .inverse-display-band,
  .animation-band,
  .matrix-stage,
  .method-stage {
    grid-template-columns: 1fr;
  }

  .verification-grid {
    grid-template-columns: minmax(240px, 1fr) auto minmax(240px, 1fr) auto minmax(240px, 1fr);
    overflow-x: auto;
  }

  .verification-grid .operator-glyph {
    margin: 0;
  }

  .animation-band {
    grid-template-rows: auto minmax(0, 1fr);
  }

  .timeline {
    max-height: 132px;
  }

  .operator-glyph {
    margin: 0 auto;
  }

  .animation-band,
  .formula-box {
    min-height: 0;
    max-height: none;
    overflow: hidden;
  }

  .formula-box {
    grid-template-rows: auto auto auto minmax(0, 1fr);
  }
}

@media (max-width: 620px) {
  .app-shell {
    padding: 12px;
  }

  .workspace {
    height: calc(100dvh - 24px);
    min-height: 0;
  }

  .topbar {
    align-items: flex-start;
    flex-direction: column;
  }

  .status-strip {
    justify-content: flex-start;
  }

  .size-grid {
    grid-template-columns: auto 1fr auto 1fr;
  }

  .size-grid span:nth-of-type(3) {
    grid-column: 1;
  }
}