/* Equation Solver tab — purple diff-theme (#a855f7) */
#tab-solver .solver-workspace-panel {
  overflow: visible;
  position: relative;
  background:
    radial-gradient(ellipse 80% 50% at 0% 0%, rgba(168, 85, 247, 0.08), transparent 55%),
    radial-gradient(ellipse 60% 40% at 100% 100%, rgba(217, 70, 239, 0.06), transparent 50%);
  border: 1px solid rgba(168, 85, 247, 0.12);
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.04),
    0 8px 32px rgba(0, 0, 0, 0.25);
}

.diff-cat-pill.active.diff-theme-solver,
.diff-theme-solver .diff-cat-pill.active {
  border-color: rgba(168, 85, 247, 0.55);
  color: #c084fc;
  background: rgba(168, 85, 247, 0.12);
  box-shadow: 0 0 18px rgba(168, 85, 247, 0.28);
}
.diff-theme-solver .diff-mode-select:focus {
  outline: none;
  border-color: rgba(168, 85, 247, 0.55);
  box-shadow: 0 0 0 2px rgba(168, 85, 247, 0.15);
}
.diff-theme-solver .diff-preset-chip:hover {
  border-color: rgba(168, 85, 247, 0.35);
  background: rgba(168, 85, 247, 0.06);
}
.diff-theme-solver .diff-rail-dot.active {
  background: #a855f7;
  box-shadow: 0 0 10px rgba(168, 85, 247, 0.6);
}

.solver-trial-badge {
  margin-bottom: 0.5rem;
}

.solver-type-hint {
  margin: 0.65rem 0 1rem;
  padding: 0.55rem 0.85rem;
  border-radius: 10px;
  font-size: 0.82rem;
  line-height: 1.5;
  color: rgba(233, 213, 255, 0.75);
  background: rgba(168, 85, 247, 0.06);
  border: 1px solid rgba(168, 85, 247, 0.12);
}
.solver-type-hint code {
  font-family: 'JetBrains Mono', ui-monospace, monospace;
  font-size: 0.78rem;
  padding: 0.1rem 0.35rem;
  border-radius: 4px;
  background: rgba(168, 85, 247, 0.12);
  color: #e9d5ff;
}

.solver-main-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  align-items: start;
}

.solver-panel {
  border-radius: 14px;
  padding: 1rem 1.1rem;
  background: rgba(0, 0, 0, 0.22);
  border: 1px solid rgba(255, 255, 255, 0.06);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

.solver-panel-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.85rem;
}

.solver-panel-sub {
  margin: 0.2rem 0 0;
  font-size: 0.75rem;
  color: rgba(255, 255, 255, 0.35);
}

.solver-kbd-hint {
  flex-shrink: 0;
  padding: 0.25rem 0.55rem;
  border-radius: 6px;
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: rgba(192, 132, 252, 0.85);
  background: rgba(168, 85, 247, 0.1);
  border: 1px solid rgba(168, 85, 247, 0.2);
}

.solver-type-panels {
  position: relative;
  min-height: 120px;
}

.solver-type-panel {
  display: none;
  animation: solverPanelIn 0.28s ease forwards;
}
.solver-type-panel.active {
  display: block;
}

@keyframes solverPanelIn {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.solver-input-glass,
.solver-coeff-glass,
.solver-system-glass {
  border-radius: 12px;
  padding: 0.65rem 0.75rem;
  background: linear-gradient(145deg, rgba(168, 85, 247, 0.05), rgba(0, 0, 0, 0.28));
  border: 1px solid rgba(168, 85, 247, 0.18);
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.06);
}

.solver-input-glass {
  padding: 0.35rem;
}
.solver-input-glass .calc-input {
  border: none;
  background: transparent;
  box-shadow: none;
  min-height: 52px;
}
.solver-input-glass .calc-input:focus {
  outline: none;
  box-shadow: none;
}
.solver-input-glass:focus-within {
  border-color: rgba(168, 85, 247, 0.45);
  box-shadow:
    inset 0 1px 0 rgba(255, 255, 255, 0.06),
    0 0 0 2px rgba(168, 85, 247, 0.12);
}

.solver-coeff-in {
  width: 52px !important;
  text-align: center;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.solver-coeff-in:focus {
  outline: none;
  border-color: rgba(168, 85, 247, 0.55) !important;
  box-shadow: 0 0 0 2px rgba(168, 85, 247, 0.15);
}

.solver-coeff-row {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  flex-wrap: wrap;
  font-size: 0.88rem;
  color: rgba(255, 255, 255, 0.65);
}
.solver-coeff-row--compact {
  font-size: 0.8rem;
  gap: 0.28rem;
}
.solver-coeff-row--compact .solver-coeff-in {
  width: 44px !important;
}

.solver-system-glass {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.solver-system-row {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.55);
  flex-wrap: wrap;
}

.solver-eq-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.35rem;
  height: 1.35rem;
  border-radius: 50%;
  font-size: 0.65rem;
  font-weight: 700;
  color: #c084fc;
  background: rgba(168, 85, 247, 0.12);
  border: 1px solid rgba(168, 85, 247, 0.25);
  flex-shrink: 0;
}

.solver-preview-wrap {
  margin-top: 0.65rem;
}

.solver-preview-label {
  display: block;
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: rgba(192, 132, 252, 0.55);
  margin-bottom: 0.3rem;
}

.solver-live-preview {
  min-height: 40px;
  padding: 0.55rem 0.75rem;
  border-radius: 8px;
  background: rgba(168, 85, 247, 0.02);
  border: 1px dashed rgba(168, 85, 247, 0.12);
  color: rgba(255, 255, 255, 0.35);
  font-size: 0.85rem;
  transition: border-color 0.2s, background 0.2s;
}
.solver-live-preview.has-content {
  border-color: rgba(168, 85, 247, 0.28);
  border-style: solid;
  background: rgba(168, 85, 247, 0.05);
  color: rgba(255, 255, 255, 0.7);
}
.solver-live-preview .katex {
  font-size: 1.05rem;
  color: rgba(233, 213, 255, 0.9);
}

.solver-toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
  padding-top: 0.85rem;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
}

.solver-run-btn {
  background: linear-gradient(135deg, #a855f7, #d946ef) !important;
  box-shadow: 0 4px 18px rgba(168, 85, 247, 0.3) !important;
  min-width: 120px;
}
.solver-run-btn:hover {
  box-shadow: 0 6px 22px rgba(168, 85, 247, 0.4) !important;
  transform: translateY(-1px);
}
.solver-run-btn:active {
  transform: translateY(0);
}

.solver-clear-btn {
  border-color: rgba(168, 85, 247, 0.2) !important;
  color: rgba(192, 132, 252, 0.85) !important;
}
.solver-clear-btn:hover {
  background: rgba(168, 85, 247, 0.08) !important;
  border-color: rgba(168, 85, 247, 0.35) !important;
}

#solverSolve.loading,
.solver-run-btn.loading {
  pointer-events: none;
  position: relative;
}
#solverSolve.loading::after,
.solver-run-btn.loading::after {
  content: '';
  position: absolute;
  inset: -2px;
  border-radius: inherit;
  border: 2px solid transparent;
  border-top-color: #c084fc;
  animation: diffSpin 0.8s linear infinite;
}

.solver-ineq-details {
  margin-top: 1rem;
  border-radius: 12px;
  border: 1px solid rgba(168, 85, 247, 0.12);
  background: rgba(168, 85, 247, 0.03);
  overflow: hidden;
}
.solver-ineq-summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.65rem 0.85rem;
  cursor: pointer;
  font-size: 0.82rem;
  font-weight: 600;
  color: rgba(192, 132, 252, 0.9);
  list-style: none;
  user-select: none;
}
.solver-ineq-summary::-webkit-details-marker {
  display: none;
}
.solver-ineq-chevron {
  width: 0.45rem;
  height: 0.45rem;
  border-right: 2px solid rgba(192, 132, 252, 0.7);
  border-bottom: 2px solid rgba(192, 132, 252, 0.7);
  transform: rotate(45deg);
  transition: transform 0.2s;
  margin-top: -0.15rem;
}
.solver-ineq-details[open] .solver-ineq-chevron {
  transform: rotate(-135deg);
  margin-top: 0.15rem;
}
.solver-ineq-body {
  padding: 0 0.85rem 0.85rem;
  border-top: 1px solid rgba(168, 85, 247, 0.08);
}
.solver-ineq-actions {
  margin-top: 0.65rem;
}
.solver-ineq-input {
  flex: 1;
  min-width: 140px;
  max-width: none !important;
}
.solver-ineq-result {
  margin-top: 0.55rem;
  padding: 0.65rem 0.75rem;
  border-radius: 8px;
  background: rgba(0, 0, 0, 0.2);
  border: 1px solid rgba(168, 85, 247, 0.1);
  font-size: 0.88rem;
}
.solver-ineq-result .result-value {
  color: #c084fc;
}

.solver-mini-btn {
  border-color: rgba(168, 85, 247, 0.22) !important;
  color: rgba(192, 132, 252, 0.88) !important;
}
.solver-mini-btn:hover {
  background: rgba(168, 85, 247, 0.1) !important;
  border-color: rgba(168, 85, 247, 0.4) !important;
}

.solver-result-body {
  min-height: 100px;
  position: relative;
}
.solver-result-body.has-result {
  min-height: auto;
}

.solver-empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 1.5rem 1rem;
  color: rgba(255, 255, 255, 0.35);
}
.solver-empty-icon {
  width: 2.5rem;
  height: 2.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 12px;
  font-size: 1.25rem;
  font-weight: 800;
  color: rgba(168, 85, 247, 0.6);
  background: rgba(168, 85, 247, 0.08);
  border: 1px dashed rgba(168, 85, 247, 0.25);
  margin-bottom: 0.65rem;
}
.solver-empty-state p {
  margin: 0;
  font-size: 0.88rem;
}
.solver-empty-sub {
  margin-top: 0.35rem !important;
  font-size: 0.75rem !important;
  color: rgba(255, 255, 255, 0.25) !important;
}

.solver-copy-btn {
  flex-shrink: 0;
  padding: 0.3rem 0.65rem;
  border-radius: 8px;
  border: 1px solid rgba(168, 85, 247, 0.2);
  background: rgba(168, 85, 247, 0.06);
  color: rgba(192, 132, 252, 0.85);
  font-size: 0.72rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}
.solver-copy-btn:hover:not(:disabled) {
  background: rgba(168, 85, 247, 0.14);
  border-color: rgba(168, 85, 247, 0.4);
  color: #e9d5ff;
}
.solver-copy-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}
.solver-copy-btn.copied {
  color: #22c55e;
  border-color: rgba(34, 197, 94, 0.35);
  background: rgba(34, 197, 94, 0.08);
}

.solution-card {
  padding: 0.7rem 0.9rem;
  margin-bottom: 0.45rem;
  border-radius: 10px;
  background: linear-gradient(135deg, rgba(168, 85, 247, 0.1), rgba(168, 85, 247, 0.04));
  border: 1px solid rgba(168, 85, 247, 0.2);
  opacity: 0;
  transform: translateY(8px);
  animation: stepFadeUp 0.4s ease forwards;
}
.solution-val {
  font-family: 'JetBrains Mono', ui-monospace, monospace;
  font-size: 0.95rem;
  color: #e9d5ff;
  line-height: 1.45;
}

.solver-error-msg {
  padding: 0.65rem 0.85rem;
  border-radius: 10px;
  font-size: 0.88rem;
  color: #fca5a5;
  background: rgba(239, 68, 68, 0.08);
  border: 1px solid rgba(239, 68, 68, 0.2);
}

.solver-warn-msg {
  padding: 0.65rem 0.85rem;
  border-radius: 10px;
  font-size: 0.88rem;
  color: #fdba74;
  background: rgba(251, 146, 60, 0.08);
  border: 1px solid rgba(251, 146, 60, 0.2);
}

.solver-graph-wrap {
  margin-top: 0.75rem;
}
.solver-graph-wrap[hidden] {
  display: none !important;
}

.solver-graph-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  border: 1px solid rgba(168, 85, 247, 0.35);
  background: rgba(168, 85, 247, 0.08);
  color: #c084fc;
  font-family: inherit;
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}
.solver-graph-btn:hover {
  background: rgba(168, 85, 247, 0.16);
  border-color: rgba(168, 85, 247, 0.55);
  box-shadow: 0 0 16px rgba(168, 85, 247, 0.15);
  color: #e9d5ff;
}

.solver-steps-section {
  margin-top: 1.25rem;
  padding-top: 1rem;
  border-top: 1px solid rgba(168, 85, 247, 0.1);
}

.solver-steps-head {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.65rem;
}

.solver-steps-title {
  margin: 0;
  font-size: 0.92rem;
  font-weight: 700;
  color: rgba(255, 255, 255, 0.85);
  letter-spacing: 0.01em;
}

.solver-steps-badge {
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
  font-size: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: rgba(192, 132, 252, 0.9);
  background: rgba(168, 85, 247, 0.1);
  border: 1px solid rgba(168, 85, 247, 0.22);
}

#solverStepsHost:empty::before {
  content: 'Solve an equation to see the full walkthrough here.';
  display: block;
  padding: 1rem;
  border-radius: 10px;
  font-size: 0.82rem;
  color: rgba(255, 255, 255, 0.28);
  text-align: center;
  border: 1px dashed rgba(168, 85, 247, 0.12);
  background: rgba(168, 85, 247, 0.02);
}

@media (max-width: 768px) {
  .solver-main-grid {
    grid-template-columns: 1fr;
  }
  .solver-toolbar {
    position: sticky;
    bottom: 0.5rem;
    z-index: 2;
    margin-top: 0.85rem;
    padding: 0.65rem;
    border-radius: 12px;
    background: rgba(8, 12, 24, 0.92);
    border: 1px solid rgba(168, 85, 247, 0.15);
    box-shadow: 0 -4px 24px rgba(0, 0, 0, 0.35);
  }
  .solver-run-btn {
    flex: 1;
  }
}

@media (max-width: 640px) {
  #tab-solver .diff-enhance-strip {
    gap: 0.25rem;
  }
  #tab-solver .diff-cat-pill {
    font-size: 0.72rem;
    padding: 0.35rem 0.55rem;
  }
  .solver-kbd-hint {
    display: none;
  }
  .solver-coeff-row--compact .solver-coeff-in {
    width: 40px !important;
  }
}