/* Shielding Paint & Window Films Lesson CSS */
#paint-lesson {
  margin-top: 1.5rem;
}

.lesson-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--line);
  padding-bottom: 0.75rem;
}

.tab-btn {
  background: var(--paper);
  border: 1px solid var(--line);
  padding: 0.5rem 0.9rem;
  border-radius: 6px;
  font-family: inherit;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--ink);
  cursor: pointer;
  transition: all 0.2s ease;
}

.tab-btn:hover {
  background: #e8ecf2;
}

.tab-btn.active {
  background: var(--blue);
  color: #fff;
  border-color: var(--blue);
}

.lesson-panel {
  display: none;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 1.75rem;
  margin-bottom: 1.5rem;
  box-shadow: 0 2px 8px rgba(21, 34, 57, 0.04);
}

.lesson-panel.active {
  display: block;
}

.lesson-panel h2 {
  font-size: 1.4rem;
  margin-top: 0;
  margin-bottom: 0.5rem;
  color: var(--ink);
}

.panel-subtitle {
  color: #556987;
  font-size: 0.95rem;
  margin-bottom: 1.5rem;
  line-height: 1.5;
}

/* Chapter 1: Materials Grid */
.material-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.mat-card {
  border: 2px solid var(--line);
  border-radius: 8px;
  padding: 1.25rem;
  background: var(--paper);
  cursor: pointer;
  transition: all 0.2s ease;
  text-align: left;
}

.mat-card:hover {
  border-color: #a0aec0;
}

.mat-card.active {
  border-color: var(--blue);
  background: #f0f5ff;
}

.mat-icon {
  font-size: 2rem;
  display: block;
  margin-bottom: 0.4rem;
}

.mat-card h3 {
  margin: 0.2rem 0 0.4rem 0;
  font-size: 1.05rem;
  color: var(--ink);
}

.mat-tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  background: #e2e8f0;
  color: #4a5568;
}

.mat-detail-box {
  background: #0b1320;
  border-radius: 8px;
  padding: 1.5rem;
  color: #fff;
  margin-bottom: 1.5rem;
}

.mat-stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.mat-stat-card {
  background: #152239;
  border: 1px solid #23395d;
  padding: 0.85rem;
  border-radius: 6px;
}

.readout-label {
  font-size: 0.75rem;
  color: #8da4c4;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.readout-value {
  font-size: 1.35rem;
  font-weight: 700;
  color: #a8f074;
  margin-top: 0.2rem;
}

/* Chapter 2: Interactive Room Enclosure Builder */
.builder-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 1.5rem;
}

@media (max-width: 820px) {
  .builder-layout {
    grid-template-columns: 1fr;
  }
}

.builder-controls {
  background: var(--paper);
  padding: 1.25rem;
  border-radius: 8px;
  border: 1px solid var(--line);
}

.control-toggle-row {
  margin-bottom: 1rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid #e2e8f0;
}

.control-toggle-row:last-child {
  border-bottom: none;
  margin-bottom: 0;
  padding-bottom: 0;
}

.control-label {
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--ink);
  margin-bottom: 0.4rem;
  display: block;
}

.toggle-pills {
  display: flex;
  gap: 0.4rem;
  flex-wrap: wrap;
}

.pill-btn {
  background: #fff;
  border: 1px solid var(--line);
  padding: 0.4rem 0.75rem;
  border-radius: 4px;
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--ink);
  cursor: pointer;
  transition: all 0.15s;
}

.pill-btn:hover {
  background: #f1f5f9;
}

.pill-btn.active {
  background: var(--blue);
  color: #fff;
  border-color: var(--blue);
}

.room-sim-screen {
  background: #0b1320;
  border-radius: 8px;
  padding: 1.25rem;
  color: #fff;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.room-box-visual {
  height: 180px;
  border: 4px solid #475569;
  border-radius: 8px;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #0f1c2e;
  transition: all 0.3s ease;
}

.room-box-visual.paint-1 {
  border-color: #3b82f6;
  box-shadow: inset 0 0 15px rgba(59, 130, 246, 0.3);
}

.room-box-visual.paint-2 {
  border-color: #10b981;
  box-shadow: inset 0 0 25px rgba(16, 185, 129, 0.4);
}

.room-box-visual.unshielded {
  border-color: #ef4444;
}

.incident-arrow {
  position: absolute;
  left: -20px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.5rem;
  color: #ef4444;
  animation: pulseArrow 1.5s infinite;
}

@keyframes pulseArrow {
  0% { transform: translate(-5px, -50%); opacity: 0.7; }
  50% { transform: translate(5px, -50%); opacity: 1; }
  100% { transform: translate(-5px, -50%); opacity: 0.7; }
}

.inside-occupant {
  font-size: 2.2rem;
  text-align: center;
}

/* Chapter 3: Internal Wi-Fi Echo Chamber */
.echo-box {
  background: #0b1320;
  border-radius: 8px;
  padding: 1.5rem;
  color: #fff;
  margin-bottom: 1.5rem;
}

.echo-canvas-area {
  height: 160px;
  background: #060b13;
  border: 2px solid #10b981;
  border-radius: 8px;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  margin: 1rem 0;
}

.echo-waves-svg {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

/* Chapter 4: Grounding Steps */
.ground-steps-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1rem;
  margin-bottom: 1.5rem;
}

.ground-step-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 1.25rem;
  background: var(--paper);
}

.step-num {
  display: inline-block;
  background: var(--blue);
  color: #fff;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  text-align: center;
  line-height: 26px;
  font-weight: 700;
  font-size: 0.85rem;
  margin-bottom: 0.5rem;
}

/* Chapter 5: Quiz */
.quiz-item {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 1.25rem;
  margin-bottom: 1.25rem;
}

.quiz-question {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.75rem;
  color: var(--ink);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.quiz-opt-btn {
  background: #fff;
  border: 1px solid var(--line);
  padding: 0.75rem 1rem;
  border-radius: 6px;
  text-align: left;
  font-family: inherit;
  font-size: 0.9rem;
  color: var(--ink);
  cursor: pointer;
  transition: all 0.2s ease;
}

.quiz-opt-btn:hover {
  background: #f1f5f9;
  border-color: #94a3b8;
}

.quiz-opt-btn.correct {
  background: #dcfce7;
  border-color: #16a34a;
  color: #15803d;
  font-weight: 600;
}

.quiz-opt-btn.incorrect {
  background: #fee2e2;
  border-color: #dc2626;
  color: #991b1b;
}

.quiz-feedback {
  margin-top: 0.75rem;
  padding: 0.75rem;
  border-radius: 6px;
  font-size: 0.88rem;
  line-height: 1.4;
  display: none;
}

.quiz-feedback.show {
  display: block;
}

.feedback-correct {
  background: #dcfce7;
  color: #166534;
}

.feedback-incorrect {
  background: #fee2e2;
  color: #991b1b;
}

/* Nav Controls */
.lesson-nav-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
}

.callout-box {
  background: #f8fafc;
  border-left: 4px solid var(--blue);
  padding: 1rem 1.25rem;
  border-radius: 0 6px 6px 0;
  margin: 1.25rem 0;
  font-size: 0.92rem;
}