:root {
  --ink: #0f172a;
  --bg: #f8fafc;
  --surface: #ffffff;
  --line: #e2e8f0;
  --electric-blue: #0284c7;
  --electric-cyan: #06b6d4;
  --electric-yellow: #eab308;
  --glow-yellow: #fde047;
  --danger: #ef4444;
  --success: #10b981;
  --font-display: "Bricolage Grotesque", system-ui, sans-serif;
  --font-body: "Lexend", system-ui, sans-serif;
  --shadow: 0 10px 25px rgba(2, 132, 199, 0.08);
  --shadow-hover: 0 16px 36px rgba(2, 132, 199, 0.16);
  --radius-lg: 20px;
  --radius-md: 12px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--ink);
  line-height: 1.5;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  background: #091e3a;
  color: #fff;
  padding: 0.9rem 1.4rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
  border-bottom: 3px solid var(--electric-cyan);
  position: sticky;
  top: 0;
  z-index: 50;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  text-decoration: none;
  color: #fff;
}

.brand-icon {
  font-size: 2.2rem;
  background: rgba(6, 182, 212, 0.2);
  padding: 0.4rem;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.brand h1 {
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 800;
  color: #7dd3fc;
  letter-spacing: -0.01em;
}

.brand p {
  font-size: 0.8rem;
  color: #bae6fd;
}

.controls-bar {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  flex-wrap: wrap;
}

.tab-pills {
  display: flex;
  background: rgba(0, 0, 0, 0.25);
  padding: 0.25rem;
  border-radius: 999px;
  gap: 0.3rem;
}

.tab-btn {
  background: transparent;
  border: none;
  color: #bae6fd;
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 700;
  padding: 0.45rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  transition: all 0.2s;
}

.tab-btn:hover {
  color: #fff;
}

.tab-btn.active {
  background: var(--electric-cyan);
  color: #091e3a;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

.btn-header {
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
  border: 1px solid rgba(255, 255, 255, 0.2);
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  font-family: var(--font-body);
  font-size: 0.82rem;
  font-weight: 700;
  text-decoration: none;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  transition: all 0.2s;
}

.btn-header:hover {
  background: rgba(255, 255, 255, 0.25);
}

.game-container {
  max-width: 1200px;
  margin: 1.5rem auto;
  padding: 0 1.2rem;
  width: 100%;
  flex: 1;
}

.tab-pane {
  display: none;
  animation: fadeIn 0.25s ease-out;
}

.tab-pane.active {
  display: block;
}

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

.section-intro {
  margin-bottom: 1.5rem;
}

.section-intro h2 {
  font-family: var(--font-display);
  font-size: 1.5rem;
  color: #0c4a6e;
}

.section-desc {
  color: #475569;
  font-size: 0.95rem;
  margin-top: 0.3rem;
}

/* ================== TAB 1: CIRCUIT BUILDER ================== */
.builder-layout {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 1.5rem;
}

.palette {
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.2rem;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
}

.palette h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  color: #0c4a6e;
}

.palette-sub {
  font-size: 0.8rem;
  color: #64748b;
  margin-bottom: 0.4rem;
}

.palette-items {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.palette-btn {
  background: #f8fafc;
  border: 1.5px solid #cbd5e1;
  border-radius: var(--radius-md);
  padding: 0.65rem 0.8rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--ink);
  cursor: pointer;
  transition: all 0.2s;
  text-align: left;
}

.palette-btn:hover {
  background: #f0fdf4;
  border-color: var(--electric-blue);
  transform: translateX(3px);
}

.comp-icon {
  font-size: 1.4rem;
}

.circuit-actions {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  margin-top: 1rem;
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}

.btn-action {
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 800;
  background: var(--electric-blue);
  color: #fff;
  border: none;
  padding: 0.6rem 1.2rem;
  border-radius: 999px;
  cursor: pointer;
  transition: all 0.2s;
  text-align: center;
}

.btn-action:hover {
  background: #0369a1;
  transform: translateY(-2px);
}

.btn-danger {
  background: #fee2e2;
  color: #dc2626;
  border: 1px solid #fca5a5;
}

.btn-danger:hover {
  background: #fecaca;
}

.btn-secondary {
  background: #f1f5f9;
  color: #334155;
  border: 1px solid #cbd5e1;
}

.btn-secondary:hover {
  background: #e2e8f0;
}

.board-container {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
}

.board-hud {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background: #ffffff;
  padding: 0.75rem 1.2rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--line);
  flex-wrap: wrap;
  gap: 0.8rem;
}

.hud-indicator {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 700;
  font-size: 0.92rem;
}

.status-dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  display: inline-block;
}

.dot-off { background: #94a3b8; }
.dot-on {
  background: #10b981;
  box-shadow: 0 0 10px #10b981;
}
.dot-warn {
  background: #ef4444;
  box-shadow: 0 0 10px #ef4444;
  animation: blink 0.6s infinite;
}

@keyframes blink {
  50% { opacity: 0.3; }
}

.hud-stats {
  display: flex;
  gap: 1.2rem;
  font-size: 0.88rem;
  color: #475569;
}

.hud-stats strong {
  color: #0c4a6e;
}

.canvas-wrap {
  position: relative;
  background: #0f172a;
  border: 3px solid #1e293b;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: inset 0 4px 20px rgba(0, 0, 0, 0.4);
}

#circuit-canvas {
  display: block;
  width: 100%;
  height: 460px;
}

.components-layer {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

.circuit-node-el {
  position: absolute;
  transform: translate(-50%, -50%);
  pointer-events: auto;
  cursor: pointer;
  background: #1e293b;
  border: 2px solid #38bdf8;
  border-radius: 12px;
  padding: 0.4rem 0.6rem;
  display: flex;
  align-items: center;
  gap: 0.4rem;
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  user-select: none;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
  transition: transform 0.15s, border-color 0.15s;
}

.circuit-node-el:hover {
  transform: translate(-50%, -50%) scale(1.06);
  border-color: #facc15;
}

.circuit-node-el.bulb.glowing {
  box-shadow: 0 0 25px #fde047, inset 0 0 10px #fde047;
  border-color: #fde047;
}

.circuit-node-el.motor.spinning .node-icon {
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  100% { transform: rotate(360deg); }
}

.board-tips {
  font-size: 0.85rem;
  color: #64748b;
  background: #f1f5f9;
  padding: 0.6rem 1rem;
  border-radius: 8px;
}

/* ================== TAB 2: CONDUCTORS & INSULATORS ================== */
.bench-stage {
  display: flex;
  flex-direction: column;
  gap: 1.8rem;
}

.test-rig {
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.rig-svg {
  width: 100%;
  max-width: 600px;
  height: 220px;
}

.test-result-box {
  margin-top: 1rem;
  text-align: center;
  padding: 1rem 1.8rem;
  border-radius: var(--radius-md);
  background: #f8fafc;
  border: 1px solid #e2e8f0;
  max-width: 500px;
  width: 100%;
}

#test-result-status {
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.15rem;
  display: block;
}

#test-result-exp {
  font-size: 0.9rem;
  color: #475569;
  margin-top: 0.3rem;
}

.materials-shelf {
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
}

.materials-shelf h3 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  color: #0c4a6e;
  margin-bottom: 1rem;
}

.materials-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(130px, 1fr));
  gap: 0.8rem;
}

.material-card {
  background: #f8fafc;
  border: 2px solid #cbd5e1;
  border-radius: var(--radius-md);
  padding: 0.8rem 0.6rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.3rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
}

.material-card:hover {
  background: #f0f9ff;
  border-color: var(--electric-blue);
  transform: translateY(-3px);
}

.material-card.tested {
  border-color: #10b981;
  background: #f0fdf4;
}

.material-icon {
  font-size: 2rem;
}

.material-name {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--ink);
}

.material-sub {
  font-size: 0.72rem;
  color: #64748b;
  font-style: italic;
}

.classification-table-wrap {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.class-column {
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.2rem;
  min-height: 200px;
}

.col-conductor { border-color: #38bdf8; background: #f0f9ff; }
.col-conductor h3 { color: #0369a1; }

.col-insulator { border-color: #f87171; background: #fff1f2; }
.col-insulator h3 { color: #be123c; }

.class-column small {
  display: block;
  color: #64748b;
  margin-bottom: 0.8rem;
}

.class-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.class-list li {
  background: #ffffff;
  padding: 0.4rem 0.8rem;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  box-shadow: 0 1px 4px rgba(0,0,0,0.05);
}

/* ================== TAB 3: CHALLENGES ================== */
.quest-layout {
  display: grid;
  grid-template-columns: 260px 1fr;
  gap: 1.5rem;
}

.quest-sidebar {
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 1.2rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.quest-btn {
  background: #f8fafc;
  border: 1.5px solid #cbd5e1;
  border-radius: var(--radius-md);
  padding: 0.7rem 0.9rem;
  font-family: var(--font-body);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--ink);
  cursor: pointer;
  text-align: left;
  transition: all 0.2s;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.quest-btn:hover {
  background: #f0f9ff;
  border-color: var(--electric-blue);
}

.quest-btn.active {
  background: #0284c7;
  color: #fff;
  border-color: #0284c7;
}

.quest-btn.done::after {
  content: "✅";
}

.quest-card {
  background: var(--surface);
  border: 2px solid var(--line);
  border-radius: var(--radius-lg);
  padding: 2.2rem;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 1.2rem;
}

.quest-badge {
  align-self: flex-start;
  font-size: 0.8rem;
  font-weight: 800;
  background: #e0f2fe;
  color: #0369a1;
  padding: 0.3rem 0.8rem;
  border-radius: 999px;
  text-transform: uppercase;
}

.quest-card h2 {
  font-family: var(--font-display);
  font-size: 1.6rem;
  color: #0c4a6e;
}

.quest-sub {
  font-size: 0.95rem;
  color: #64748b;
  font-style: italic;
}

.quest-desc {
  font-size: 1.05rem;
  color: #334155;
  background: #f8fafc;
  padding: 1.1rem;
  border-radius: var(--radius-md);
  border-left: 4px solid var(--electric-blue);
}

.quest-reqs h4 {
  font-size: 0.95rem;
  color: #0c4a6e;
  margin-bottom: 0.5rem;
}

.quest-reqs ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.quest-reqs li {
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: #475569;
}

.quest-feedback {
  font-weight: 700;
  font-size: 0.95rem;
  margin-left: 0.8rem;
}

@media (max-width: 900px) {
  .builder-layout, .quest-layout, .classification-table-wrap {
    grid-template-columns: 1fr;
  }
}