/* =============================================================================
   ILS Solver CSS — Styles for the Step-by-Step Solver
   Companion to ils-solver.js | v1.0
   Prefix: .slv- (avoids collisions with existing ILS classes)

   Sections:
     1.  Container & Header
     2.  Body Layout (Timeline + Main)
     3.  Vertical Timeline
     4.  Step Panels
     5.  Step Panel States (locked → attempt → revealed)
     6.  Working Area & Supplementary
     7.  Input Area
     8.  Controls
     9.  Summary & Celebration
    10.  Fraction Problem Layout
    11.  Mode Badge & Score
    12.  Animations (@keyframes)
    13.  Dark Mode
    14.  Responsive — 480px
    15.  Responsive — 360px
   ============================================================================= */

/* ==========================================================================
   1. CONTAINER & HEADER
   ========================================================================== */

.slv-container {
  max-width: 820px;
  margin: 0 auto;
  padding: 20px 16px 32px;
  font-family: "Nunito", "Segoe UI", system-ui, sans-serif;
  color: #334155;
  position: relative;
}

.slv-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: linear-gradient(135deg, #eef2ff 0%, #e0e7ff 100%);
  border: 2px solid #c7d2fe;
  border-radius: 16px;
  padding: 16px 20px;
  margin-bottom: 24px;
  box-shadow: 0 2px 12px rgba(99, 102, 241, 0.1);
}

.slv-problem {
  font-size: 1.25rem;
  font-weight: 800;
  color: #3730a3;
  margin-bottom: 8px;
}

.slv-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

/* ==========================================================================
   2. BODY LAYOUT (Timeline + Main Column)
   ========================================================================== */

.slv-body {
  display: flex;
  gap: 20px;
  align-items: flex-start;
}

.slv-timeline-col {
  flex: 0 0 48px;
  position: sticky;
  top: 100px;
}

.slv-main-col {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

/* ==========================================================================
   3. VERTICAL TIMELINE
   ========================================================================== */

.slv-timeline {
  display: flex;
  flex-direction: column;
  align-items: center;
}

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

.slv-tl-dot {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.8rem;
  font-weight: 800;
  border: 3px solid #cbd5e1;
  background: #f1f5f9;
  color: #94a3b8;
  transition: all 0.35s ease;
  position: relative;
  z-index: 2;
}

.slv-tl-connector {
  width: 3px;
  height: 28px;
  background: #e2e8f0;
  transition: background 0.35s ease;
}

/* Timeline dot states */
.slv-tl-active {
  border-color: #6366f1;
  background: #6366f1;
  color: #fff;
  box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.2);
  animation: slvTimelinePulse 2s ease-in-out infinite;
}

.slv-tl-done {
  border-color: #94a3b8;
  background: #e2e8f0;
  color: #64748b;
}

.slv-tl-done.slv-tl-correct {
  border-color: #22c55e;
  background: #22c55e;
  color: #fff;
}

.slv-tl-done.slv-tl-wrong {
  border-color: #ef4444;
  background: #ef4444;
  color: #fff;
}

.slv-tl-locked {
  opacity: 0.45;
}

/* Connector color follows completion */
.slv-tl-item:has(.slv-tl-done) + .slv-tl-item .slv-tl-connector,
.slv-tl-item .slv-tl-done ~ .slv-tl-connector {
  background: #94a3b8;
}

/* ==========================================================================
   4. STEP PANELS
   ========================================================================== */

.slv-step {
  background: #f8fafc;
  border: 2px solid #e2e8f0;
  border-radius: 14px;
  padding: 20px;
  transition: all 0.35s ease;
  position: relative;
  overflow: hidden;
}

.slv-step-num {
  font-size: 0.7rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 1.2px;
  color: #94a3b8;
  margin-bottom: 6px;
}

.slv-step-instruction {
  font-size: 1.05rem;
  font-weight: 700;
  color: #334155;
  margin-bottom: 14px;
  line-height: 1.5;
}

/* ==========================================================================
   5. STEP PANEL STATES
   ========================================================================== */

/* Locked — greyed out, content hidden */
.slv-step.slv-step-locked {
  opacity: 0.35;
  pointer-events: none;
  filter: grayscale(0.4);
  transform: scale(0.97);
}

/* Attempt — active, prominent border */
.slv-step.slv-step-attempt {
  border-color: #6366f1;
  background: linear-gradient(135deg, #eef2ff 0%, #f5f3ff 100%);
  box-shadow: 0 0 20px rgba(99, 102, 241, 0.12);
}

.slv-step.slv-step-attempt .slv-step-num {
  color: #6366f1;
}

/* Active (current step, any state) */
.slv-step.slv-step-active {
  animation: slvStepSlideIn 0.4s ease-out;
}

/* Revealed — correct */
.slv-step.slv-step-revealed.slv-step-correct {
  border-color: #22c55e;
  background: linear-gradient(135deg, #dcfce7 0%, #f0fdf4 100%);
}

.slv-step.slv-step-revealed.slv-step-correct .slv-step-num {
  color: #16a34a;
}

/* Revealed — wrong */
.slv-step.slv-step-revealed.slv-step-wrong {
  border-color: #ef4444;
  background: linear-gradient(135deg, #fee2e2 0%, #fef2f2 100%);
}

.slv-step.slv-step-revealed.slv-step-wrong .slv-step-num {
  color: #dc2626;
}

/* Revealed — skipped (no attempt, just revealed) */
.slv-step.slv-step-revealed.slv-step-skipped {
  border-color: #f59e0b;
  background: linear-gradient(135deg, #fffbeb 0%, #fefce8 100%);
}

.slv-step.slv-step-revealed.slv-step-skipped .slv-step-num {
  color: #d97706;
}

/* ==========================================================================
   6. WORKING AREA & SUPPLEMENTARY
   ========================================================================== */

.slv-working {
  margin: 12px 0 16px;
  padding: 16px;
  background: #fff;
  border: 1px solid #e2e8f0;
  border-radius: 10px;
  overflow-x: auto;
  text-align: center;
}

.slv-supplementary {
  margin: 8px 0 12px;
  display: flex;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
}

.slv-katex {
  font-size: 1.15rem;
  padding: 12px;
  text-align: center;
}

/* JSXGraph board inside working area */
.slv-working-jxg {
  padding: 12px 8px;
}

.slv-jxg-board {
  border: 1px solid #e2e8f0;
  border-radius: 8px;
  overflow: hidden;
  margin: 8px auto 0;
  max-width: 100%;
}

.slv-jxg-board .JXG_navigation {
  display: none;
}

.slv-jxg-equation {
  text-align: center;
}

.slv-katex-row {
  font-size: 1.2rem;
  font-weight: 800;
  color: #3730a3;
  padding: 6px 0 4px;
  letter-spacing: 0.5px;
}

/* ==========================================================================
   7. INPUT AREA
   ========================================================================== */

.slv-input-area {
  margin-top: 12px;
  animation: slvStepReveal 0.35s ease-out;
}

.slv-text-input-wrap,
.slv-frac-input-wrap {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}

.slv-answer-input {
  min-width: 80px;
  max-width: 160px;
  font-size: 1.2rem;
  font-weight: 700;
  text-align: center;
  padding: 8px 12px;
  border: 2px solid #c7d2fe;
  border-radius: 10px;
  background: #fff;
  color: #334155;
  outline: none;
  transition:
    border-color 0.25s ease,
    box-shadow 0.25s ease;
}

.slv-answer-input:focus {
  border-color: #6366f1;
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.slv-btn-submit,
.slv-btn-confirm {
  font-weight: 700;
  font-size: 0.95rem;
  padding: 8px 18px;
  border-radius: 10px;
}

.slv-input-actions {
  display: flex;
  gap: 8px;
  margin-top: 10px;
  flex-wrap: wrap;
}

.slv-btn-hint {
  background: #fef3c7;
  color: #92400e;
  border: 2px solid #fcd34d;
  border-radius: 10px;
  font-weight: 700;
  font-size: 0.85rem;
  padding: 6px 14px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.slv-btn-hint:hover {
  background: #fde68a;
  border-color: #f59e0b;
}

.slv-btn-reveal {
  background: #f1f5f9;
  color: #64748b;
  border: 2px solid #e2e8f0;
  border-radius: 10px;
  font-weight: 700;
  font-size: 0.85rem;
  padding: 6px 14px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.slv-btn-reveal:hover {
  background: #e2e8f0;
  border-color: #cbd5e1;
}

/* Choices */
.slv-choices {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}

.slv-choice-btn {
  min-width: 60px;
  font-weight: 700;
}

/* ==========================================================================
   8. REVEALED ANSWER & EXPLANATION
   ========================================================================== */

.slv-revealed {
  margin-top: 12px;
  animation: slvExplainFade 0.4s ease-out;
}

.slv-your-answer {
  font-size: 0.9rem;
  padding: 6px 12px;
  border-radius: 8px;
  margin-bottom: 8px;
  display: inline-block;
}

.slv-your-answer-correct {
  background: #dcfce7;
  color: #166534;
}

.slv-your-answer-wrong {
  background: #fee2e2;
  color: #991b1b;
}

.slv-correct-answer {
  font-size: 1rem;
  font-weight: 700;
  color: #16a34a;
  margin-bottom: 10px;
}

/* ==========================================================================
   9. CONTROLS (Navigation)
   ========================================================================== */

.slv-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 20px;
  padding: 14px 0;
}

.slv-btn-next,
.slv-btn-finish {
  font-weight: 800;
  font-size: 1rem;
  padding: 10px 28px;
  border-radius: 12px;
}

.slv-btn-show-all {
  background: transparent;
  color: #64748b;
  border: 2px solid #e2e8f0;
  border-radius: 10px;
  font-weight: 700;
  font-size: 0.85rem;
  padding: 8px 16px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.slv-btn-show-all:hover {
  background: #f1f5f9;
  border-color: #cbd5e1;
}

/* ==========================================================================
   10. SUMMARY & CELEBRATION
   ========================================================================== */

.slv-char-celebrate {
  text-align: center;
  margin-bottom: 16px;
}

/* ==========================================================================
   11. FRACTION PROBLEM LAYOUT
   ========================================================================== */

.slv-frac-problem {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
  padding: 8px 0;
}

.slv-frac-op {
  font-size: 1.5rem;
  font-weight: 800;
  color: #6366f1;
}

/* ==========================================================================
   12. MODE BADGE & SCORE
   ========================================================================== */

.slv-mode-badge {
  display: inline-block;
  background: #6366f1;
  color: #fff;
  font-size: 0.72rem;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 1px;
  padding: 3px 10px;
  border-radius: 6px;
}

.slv-score {
  font-size: 0.9rem;
  font-weight: 700;
  color: #475569;
}

.slv-score-value {
  color: #6366f1;
  font-weight: 900;
}

/* ==========================================================================
   13. ANIMATIONS (@keyframes)
   ========================================================================== */

@keyframes slvStepSlideIn {
  0% {
    opacity: 0;
    transform: translateY(16px);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slvStepReveal {
  0% {
    opacity: 0;
    transform: translateY(8px);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slvTimelinePulse {
  0%,
  100% {
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.2);
  }
  50% {
    box-shadow: 0 0 0 8px rgba(99, 102, 241, 0.1);
  }
}

@keyframes slvExplainFade {
  0% {
    opacity: 0;
    transform: translateY(6px);
  }
  100% {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slvDigitPop {
  0% {
    transform: scale(0.5);
    opacity: 0;
  }
  70% {
    transform: scale(1.15);
  }
  100% {
    transform: scale(1);
    opacity: 1;
  }
}

/* ==========================================================================
   13b. PHASE 0: MULTI-INPUT LAYOUT
   ========================================================================== */

.slv-multi-input-wrap {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}

.slv-multi-input-wrap label {
  font-weight: 700;
  font-size: 0.95rem;
  color: #475569;
  display: flex;
  align-items: center;
  gap: 6px;
}

.slv-multi-input {
  width: 80px;
}

/* ==========================================================================
   14. DARK MODE
   ========================================================================== */

.dark .slv-container {
  color: #e2e8f0;
}

.dark .slv-header {
  background: linear-gradient(135deg, #1e1b4b 0%, #312e81 100%);
  border-color: #4338ca;
  box-shadow: 0 2px 12px rgba(99, 102, 241, 0.15);
}

.dark .slv-problem {
  color: #a5b4fc;
}

/* Dark: Step panels */
.dark .slv-step {
  background: #1e293b;
  border-color: #334155;
}

.dark .slv-step-num {
  color: #64748b;
}

.dark .slv-step-instruction {
  color: #e2e8f0;
}

.dark .slv-step.slv-step-attempt {
  border-color: #818cf8;
  background: linear-gradient(135deg, #1e1b4b 0%, #1e293b 100%);
  box-shadow: 0 0 20px rgba(99, 102, 241, 0.15);
}

.dark .slv-step.slv-step-attempt .slv-step-num {
  color: #818cf8;
}

.dark .slv-step.slv-step-revealed.slv-step-correct {
  border-color: #22c55e;
  background: linear-gradient(135deg, #052e16 0%, #1e293b 100%);
}

.dark .slv-step.slv-step-revealed.slv-step-correct .slv-step-num {
  color: #4ade80;
}

.dark .slv-step.slv-step-revealed.slv-step-wrong {
  border-color: #ef4444;
  background: linear-gradient(135deg, #450a0a 0%, #1e293b 100%);
}

.dark .slv-step.slv-step-revealed.slv-step-wrong .slv-step-num {
  color: #f87171;
}

.dark .slv-step.slv-step-revealed.slv-step-skipped {
  border-color: #f59e0b;
  background: linear-gradient(135deg, #451a03 0%, #1e293b 100%);
}

.dark .slv-step.slv-step-revealed.slv-step-skipped .slv-step-num {
  color: #fbbf24;
}

/* Dark: Working area */
.dark .slv-working {
  background: #0f172a;
  border-color: #334155;
}

.dark .slv-jxg-board {
  border-color: #334155;
}

.dark .slv-katex-row {
  color: #a5b4fc;
}

/* Dark: Timeline */
.dark .slv-tl-dot {
  border-color: #475569;
  background: #334155;
  color: #64748b;
}

.dark .slv-tl-connector {
  background: #334155;
}

.dark .slv-tl-active {
  border-color: #818cf8;
  background: #818cf8;
  color: #fff;
  box-shadow: 0 0 0 4px rgba(129, 140, 248, 0.25);
}

.dark .slv-tl-done {
  border-color: #64748b;
  background: #475569;
  color: #94a3b8;
}

.dark .slv-tl-done.slv-tl-correct {
  border-color: #22c55e;
  background: #22c55e;
  color: #fff;
}

.dark .slv-tl-done.slv-tl-wrong {
  border-color: #ef4444;
  background: #ef4444;
  color: #fff;
}

/* Dark: Input area */
.dark .slv-answer-input {
  background: #0f172a;
  border-color: #4338ca;
  color: #e2e8f0;
}

.dark .slv-answer-input:focus {
  border-color: #818cf8;
  box-shadow: 0 0 0 3px rgba(129, 140, 248, 0.25);
}

.dark .slv-btn-hint {
  background: #451a03;
  color: #fbbf24;
  border-color: #92400e;
}

.dark .slv-btn-hint:hover {
  background: #78350f;
  border-color: #b45309;
}

.dark .slv-btn-reveal {
  background: #1e293b;
  color: #94a3b8;
  border-color: #334155;
}

.dark .slv-btn-reveal:hover {
  background: #334155;
  border-color: #475569;
}

/* Dark: Revealed answer */
.dark .slv-your-answer-correct {
  background: #052e16;
  color: #4ade80;
}

.dark .slv-your-answer-wrong {
  background: #450a0a;
  color: #fca5a5;
}

.dark .slv-correct-answer {
  color: #4ade80;
}

/* Dark: Controls */
.dark .slv-btn-show-all {
  background: transparent;
  color: #94a3b8;
  border-color: #334155;
}

.dark .slv-btn-show-all:hover {
  background: #1e293b;
  border-color: #475569;
}

/* Dark: Score / meta */
.dark .slv-score {
  color: #94a3b8;
}

.dark .slv-score-value {
  color: #a5b4fc;
}

.dark .slv-mode-badge {
  background: #4338ca;
}

.dark .slv-frac-op {
  color: #a5b4fc;
}

/* Dark: Phase 0 multi-input */
.dark .slv-multi-input-wrap label {
  color: #94a3b8;
}

/* Dark: Number Theory visuals (factor ladder, divisibility, Euclid) */
.dark .slv-factor-ladder,
.dark .slv-equation-display {
  --slv-factor-bg: #1e293b;
  --slv-factor-border: #334155;
  --slv-factor-line: #475569;
  --slv-factor-prime: #a5b4fc;
  --slv-factor-result: #4ade80;
  --slv-highlight-bg: #422006;
  --slv-highlight-text: #fbbf24;
}

/* ==========================================================================
   13c. STATISTICS & PROBABILITY VISUALS
   ========================================================================== */

/* ---- Bar Chart ---- */
.slv-bar-chart {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 12px 8px 4px;
}

.slv-bar-chart-title {
  font-size: 0.85rem;
  font-weight: 700;
  color: #475569;
  text-align: center;
  margin-bottom: 4px;
}

.slv-bar-chart-body {
  display: flex;
  align-items: flex-end;
  gap: 0;
  flex: 1;
  width: 100%;
}

.slv-bar-chart-ylabel {
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  font-size: 0.72rem;
  color: #64748b;
  padding-right: 4px;
  text-align: center;
}

.slv-bar-chart-bars {
  display: flex;
  align-items: flex-end;
  justify-content: center;
  gap: 6px;
  flex: 1;
  height: 100%;
  border-left: 2px solid #cbd5e1;
  border-bottom: 2px solid #cbd5e1;
  padding: 4px 8px 0;
}

.slv-bar-col {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-end;
  flex: 1;
  max-width: 48px;
  height: 100%;
}

.slv-bar-value {
  font-size: 0.72rem;
  font-weight: 700;
  color: #475569;
  margin-bottom: 2px;
}

.slv-bar {
  width: 100%;
  min-height: 4px;
  background: #818cf8;
  border-radius: 4px 4px 0 0;
  transition: height 0.3s ease;
}

.slv-bar-highlight {
  background: #f59e0b;
  box-shadow: 0 0 0 2px rgba(245, 158, 11, 0.3);
}

.slv-bar-label {
  font-size: 0.7rem;
  color: #64748b;
  margin-top: 4px;
  text-align: center;
  word-break: break-all;
}

.slv-bar-chart-xlabel {
  font-size: 0.72rem;
  color: #64748b;
  text-align: center;
  margin-top: 2px;
}

/* ---- Statistics Table ---- */
.slv-stat-table-wrap {
  overflow-x: auto;
  margin: 8px 0;
}

.slv-stat-table-title {
  font-size: 0.85rem;
  font-weight: 700;
  color: #475569;
  text-align: center;
  margin-bottom: 6px;
}

.slv-stat-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

.slv-stat-table th,
.slv-stat-table td {
  border: 1px solid #e2e8f0;
  padding: 6px 10px;
  text-align: center;
}

.slv-stat-table th {
  background: #f1f5f9;
  color: #334155;
  font-weight: 700;
  font-size: 0.8rem;
}

.slv-stat-table td {
  color: #475569;
}

.slv-stat-highlight-row {
  background: #fef3c7 !important;
}

.slv-stat-highlight-row-cell {
  background: #fef3c7;
}

.slv-stat-highlight-col {
  background: #ede9fe;
}

.slv-stat-highlight-cell {
  background: #fbbf24 !important;
  color: #78350f !important;
  font-weight: 700;
}

.slv-stat-totals-row td {
  background: #f8fafc;
  border-top: 2px solid #94a3b8;
}

/* ---- Sample Space Grid (two-dice) ---- */
.slv-sample-space th,
.slv-sample-space td {
  padding: 3px 5px;
  font-size: 0.72rem;
}

/* ---- Probability display ---- */
.slv-prob-display {
  font-size: 0.9rem;
  line-height: 1.7;
}

.slv-prob-formula {
  margin-top: 8px;
  font-size: 1rem;
  font-weight: 600;
  color: #4f46e5;
}

/* ---- Stat fraction display ---- */
.slv-stat-frac {
  font-size: 1.05em;
  font-weight: 700;
  color: #4f46e5;
}

.slv-stat-frac sup,
.slv-stat-frac sub {
  font-size: 0.85em;
}

/* ---- Stat formula block ---- */
.slv-stat-formula {
  font-size: 0.95rem;
  line-height: 1.8;
  padding: 6px 0;
}

/* ---- Stat info block (below tables) ---- */
.slv-stat-info {
  margin-top: 8px;
  padding: 8px 12px;
  background: #f0fdf4;
  border-left: 3px solid #22c55e;
  border-radius: 4px;
  font-size: 0.88rem;
  color: #166534;
}

/* ---- Stat highlight span (sorted data) ---- */
.slv-stat-highlight {
  display: inline-block;
  background: #fbbf24;
  color: #78350f;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: 4px;
  margin: 0 1px;
}

/* ---- Dark Mode: Statistics & Probability ---- */
.dark .slv-bar-chart-title,
.dark .slv-stat-table-title {
  color: #94a3b8;
}

.dark .slv-bar-value {
  color: #94a3b8;
}

.dark .slv-bar {
  background: #6366f1;
}

.dark .slv-bar-highlight {
  background: #f59e0b;
  box-shadow: 0 0 0 2px rgba(245, 158, 11, 0.25);
}

.dark .slv-bar-label,
.dark .slv-bar-chart-xlabel,
.dark .slv-bar-chart-ylabel {
  color: #64748b;
}

.dark .slv-bar-chart-bars {
  border-left-color: #475569;
  border-bottom-color: #475569;
}

.dark .slv-stat-table th {
  background: #1e293b;
  color: #cbd5e1;
  border-color: #334155;
}

.dark .slv-stat-table td {
  color: #94a3b8;
  border-color: #334155;
}

.dark .slv-stat-highlight-row {
  background: #422006 !important;
}

.dark .slv-stat-highlight-row-cell {
  background: #422006;
}

.dark .slv-stat-highlight-col {
  background: #2e1065;
}

.dark .slv-stat-highlight-cell {
  background: #b45309 !important;
  color: #fef3c7 !important;
}

.dark .slv-stat-totals-row td {
  background: #1e293b;
  border-top-color: #475569;
}

.dark .slv-prob-formula {
  color: #a5b4fc;
}

.dark .slv-stat-frac {
  color: #a5b4fc;
}

.dark .slv-stat-formula {
  color: #e2e8f0;
}

.dark .slv-stat-info {
  background: #052e16;
  border-left-color: #16a34a;
  color: #86efac;
}

.dark .slv-stat-highlight {
  background: #b45309;
  color: #fef3c7;
}

.dark .slv-prob-display {
  color: #cbd5e1;
}

/* ==========================================================================
   15. RESPONSIVE — 480px
   ========================================================================== */

@media (max-width: 480px) {
  .slv-container {
    padding: 12px 10px 24px;
  }

  .slv-header {
    padding: 12px 14px;
    border-radius: 12px;
    margin-bottom: 16px;
  }

  .slv-problem {
    font-size: 1.05rem;
  }

  .slv-meta {
    gap: 8px;
  }

  /* Stack timeline horizontally above steps */
  .slv-body {
    flex-direction: column;
    gap: 12px;
  }

  .slv-timeline-col {
    position: static;
    flex: none;
    width: 100%;
  }

  .slv-timeline {
    flex-direction: row;
    justify-content: center;
    gap: 0;
    overflow-x: auto;
    padding: 4px 0;
  }

  .slv-tl-item {
    flex-direction: row;
    align-items: center;
  }

  .slv-tl-connector {
    width: 20px;
    height: 3px;
  }

  .slv-tl-dot {
    width: 30px;
    height: 30px;
    font-size: 0.72rem;
  }

  /* Step panels */
  .slv-step {
    padding: 14px;
    border-radius: 10px;
  }

  .slv-step-instruction {
    font-size: 0.95rem;
  }

  .slv-working {
    padding: 10px;
    border-radius: 8px;
  }

  /* Controls stack */
  .slv-controls {
    flex-direction: column;
    gap: 8px;
    padding: 10px 0;
  }

  .slv-btn-next,
  .slv-btn-finish {
    width: 100%;
    text-align: center;
  }

  .slv-btn-show-all {
    width: 100%;
    text-align: center;
  }

  /* Input adjustments */
  .slv-text-input-wrap,
  .slv-frac-input-wrap {
    flex-direction: column;
    align-items: stretch;
  }

  .slv-answer-input {
    max-width: 100%;
    width: 100%;
  }

  .slv-btn-submit,
  .slv-btn-confirm {
    width: 100%;
  }

  .slv-input-actions {
    justify-content: center;
  }
}

/* ==========================================================================
   16. RESPONSIVE — 360px
   ========================================================================== */

@media (max-width: 360px) {
  .slv-container {
    padding: 8px 6px 16px;
  }

  .slv-header {
    padding: 10px 10px;
    margin-bottom: 12px;
  }

  .slv-problem {
    font-size: 0.95rem;
  }

  .slv-step {
    padding: 10px;
  }

  .slv-step-instruction {
    font-size: 0.88rem;
  }

  .slv-tl-dot {
    width: 26px;
    height: 26px;
    font-size: 0.65rem;
    border-width: 2px;
  }

  .slv-tl-connector {
    width: 14px;
  }

  .slv-mode-badge {
    font-size: 0.65rem;
    padding: 2px 7px;
  }

  .slv-score {
    font-size: 0.8rem;
  }

  .slv-answer-input {
    font-size: 1rem;
    padding: 6px 8px;
  }

  .slv-btn-hint,
  .slv-btn-reveal {
    font-size: 0.78rem;
    padding: 5px 10px;
  }

  .slv-frac-problem {
    gap: 6px;
  }

  .slv-frac-op {
    font-size: 1.2rem;
  }
}

/* ==========================================================================
   17. DATA HANDLING — .slv-dh-*
       Styles for scatter plots, accumulator tables, equation displays and
       formula hints generated by ils-solver-gen-data-handling.js
   ========================================================================== */

/* ── Scatter plot wrapper ── */
.slv-dh-scatter-wrap {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 6px 0 2px;
}

.slv-dh-scatter-svg {
  max-width: 100%;
  border-radius: 8px;
  display: block;
}

.slv-dh-scatter-empty {
  padding: 24px;
  text-align: center;
  color: #94a3b8;
  font-size: 0.85rem;
}

/* ── Data table ── */
.slv-dh-table-wrap {
  overflow-x: auto;
  margin: 4px 0 8px;
  border-radius: 10px;
  border: 1px solid #e2e8f0;
  background: #fff;
}

.slv-dh-table-caption {
  padding: 7px 12px 4px;
  font-size: 0.78rem;
  font-weight: 700;
  color: #64748b;
  text-transform: uppercase;
  letter-spacing: 0.6px;
  border-bottom: 1px solid #f1f5f9;
}

.slv-dh-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
  font-family: "JetBrains Mono", ui-monospace, monospace;
}

.slv-dh-table thead tr {
  background: #f8fafc;
}

.slv-dh-table th {
  padding: 6px 10px;
  font-weight: 700;
  font-size: 0.78rem;
  color: #475569;
  text-align: right;
  border-bottom: 2px solid #e2e8f0;
  white-space: nowrap;
}

.slv-dh-table th:first-child {
  text-align: left;
}

.slv-dh-table td {
  padding: 5px 10px;
  text-align: right;
  color: #334155;
  border-bottom: 1px solid #f1f5f9;
}

.slv-dh-table td:first-child {
  text-align: left;
  font-weight: 600;
  color: #1e293b;
}

.slv-dh-table tbody tr:last-child td {
  border-bottom: none;
}

.slv-dh-table tbody tr:hover {
  background: #fafafa;
}

/* Highlighted columns for transformed values */
.slv-dh-table .slv-dh-col-tx,
.slv-dh-table .slv-dh-col-ty {
  background: #eff6ff;
  color: #1d4ed8;
}

.slv-dh-table .slv-dh-col-x2 {
  background: #fefce8;
  color: #92400e;
}

.slv-dh-table .slv-dh-col-xy {
  background: #f0fdf4;
  color: #14532d;
}

/* Totals / Sigma row */
.slv-dh-totals td {
  background: #f8fafc;
  border-top: 2px solid #e2e8f0 !important;
  font-weight: 700;
  color: #1e293b;
}

/* ── Accumulator display ── */
.slv-dh-accum {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  padding: 8px 12px 10px;
  background: #f8fafc;
  border-top: 1px solid #e2e8f0;
  border-radius: 0 0 10px 10px;
}

.slv-dh-accum-row {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  background: #fff;
  border: 1px solid #e2e8f0;
  border-radius: 6px;
  padding: 3px 9px;
  font-size: 0.82rem;
}

.slv-dh-accum-key {
  font-weight: 700;
  color: #4338ca;
  font-family: "JetBrains Mono", ui-monospace, monospace;
}

.slv-dh-accum-val {
  font-weight: 600;
  color: #1e293b;
  font-family: "JetBrains Mono", ui-monospace, monospace;
}

/* ── Formula hint (e.g. "Also compute Σxy = …") ── */
.slv-dh-formula-hint {
  padding: 6px 12px 8px;
  font-size: 0.82rem;
  color: #64748b;
  font-style: italic;
  border-top: 1px solid #f1f5f9;
}

/* ── Equation display (predict-from-fit) ── */
.slv-dh-eq-display {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 16px 20px;
  background: linear-gradient(135deg, #eef2ff 0%, #e0e7ff 100%);
  border: 2px solid #c7d2fe;
  border-radius: 12px;
  margin: 4px 0;
}

.slv-dh-eq-label {
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: #6366f1;
}

.slv-dh-eq-value {
  font-size: 1.05rem;
  font-weight: 700;
  color: #1e293b;
  font-family: "JetBrains Mono", ui-monospace, monospace;
}

.slv-dh-eq-r {
  font-size: 0.8rem;
  font-weight: 600;
  color: #64748b;
  font-family: "JetBrains Mono", ui-monospace, monospace;
}

/* ── Dark mode overrides ── */
.dark .slv-dh-table-wrap {
  background: #1e293b;
  border-color: #334155;
}

.dark .slv-dh-table-caption {
  color: #94a3b8;
  border-color: #334155;
}

.dark .slv-dh-table thead tr {
  background: #0f172a;
}

.dark .slv-dh-table th {
  color: #94a3b8;
  border-color: #334155;
}

.dark .slv-dh-table td {
  color: #cbd5e1;
  border-color: #1e293b;
}

.dark .slv-dh-table td:first-child {
  color: #f1f5f9;
}

.dark .slv-dh-table tbody tr:hover {
  background: #1a2740;
}

.dark .slv-dh-table .slv-dh-col-tx,
.dark .slv-dh-table .slv-dh-col-ty {
  background: #1e3a5f;
  color: #93c5fd;
}

.dark .slv-dh-table .slv-dh-col-x2 {
  background: #2d2006;
  color: #fde68a;
}

.dark .slv-dh-table .slv-dh-col-xy {
  background: #052e16;
  color: #86efac;
}

.dark .slv-dh-totals td {
  background: #0f172a;
  border-color: #334155 !important;
  color: #f1f5f9;
}

.dark .slv-dh-accum {
  background: #0f172a;
  border-color: #334155;
}

.dark .slv-dh-accum-row {
  background: #1e293b;
  border-color: #334155;
}

.dark .slv-dh-accum-key {
  color: #818cf8;
}

.dark .slv-dh-accum-val {
  color: #f1f5f9;
}

.dark .slv-dh-formula-hint {
  color: #94a3b8;
  border-color: #334155;
}

.dark .slv-dh-eq-display {
  background: linear-gradient(135deg, #1e1b4b 0%, #312e81 100%);
  border-color: #4338ca;
}

.dark .slv-dh-eq-label {
  color: #a5b4fc;
}

.dark .slv-dh-eq-value {
  color: #e0e7ff;
}

.dark .slv-dh-eq-r {
  color: #94a3b8;
}

/* ── Responsive: narrow screens ── */
@media (max-width: 480px) {
  .slv-dh-scatter-wrap {
    padding: 4px 0;
  }

  .slv-dh-scatter-svg {
    width: 100%;
    height: auto;
  }

  .slv-dh-table {
    font-size: 0.78rem;
  }

  .slv-dh-table th,
  .slv-dh-table td {
    padding: 4px 7px;
  }

  .slv-dh-accum {
    gap: 4px;
    padding: 6px 8px;
  }

  .slv-dh-accum-row {
    font-size: 0.76rem;
    padding: 2px 7px;
  }

  .slv-dh-eq-display {
    padding: 12px 14px;
  }

  .slv-dh-eq-value {
    font-size: 0.92rem;
  }
}