* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100vh;
  color: #333;
  display: flex;
  flex-direction: column;
}

.app-container {
  flex: 1;
  max-width: 1400px;
  margin: 0 auto;
  padding: 2rem;
  width: 100%;
}

.header {
  text-align: center;
  margin-bottom: 2rem;
}

.header h1 {
  color: white;
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}

.header p {
  color: rgba(255,255,255,0.9);
  font-size: 1.1rem;
}

.main-content {
  display: grid;
  grid-template-columns: 400px 1fr;
  gap: 2rem;
}

@media (max-width: 1000px) {
  .main-content {
    grid-template-columns: 1fr;
  }
}

/* Panels */
.left-panel, .right-panel {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.items-section,
.knapsack-section,
.optimal-section,
.chart-section,
.analysis-section,
.explainer-section {
  background: white;
  border-radius: 12px;
  padding: 1.5rem;
  box-shadow: 0 4px 20px rgba(0,0,0,0.15);
}

h3 {
  font-size: 1.1rem;
  color: #333;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

h3 .hint {
  font-size: 0.8rem;
  font-weight: normal;
  color: #888;
}

/* Items Grid */
.items-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 0.75rem;
}

.item-card {
  border: 3px solid #e0e0e0;
  border-radius: 10px;
  padding: 1rem;
  cursor: pointer;
  transition: all 0.2s ease;
  position: relative;
  background: #f8f9fa;
}

.item-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.item-card.selected {
  border-color: #28a745;
  background: linear-gradient(135deg, #d4edda 0%, #c3e6cb 100%);
}

.item-card.disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.item-card.disabled:hover {
  transform: none;
  box-shadow: none;
}

/* Heatmap recommendation - dotted outline */
.item-card.recommended {
  border: 3px dashed #333;
}

.item-card.recommended::after {
  content: 'ODE suggests';
  position: absolute;
  top: -10px;
  right: 8px;
  background: #667eea;
  color: white;
  font-size: 0.65rem;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 600;
}

/* Heat overlay for ODE values */
.item-heat-overlay {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity 0.3s;
  pointer-events: none;
}

.show-heatmap .item-card:not(.selected) .item-heat-overlay {
  opacity: 0.85;
}

.item-heat-value {
  font-size: 1.2rem;
  font-weight: bold;
  color: white;
  text-shadow: 1px 1px 2px rgba(0,0,0,0.5);
}

.item-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.item-icon {
  font-size: 1.5rem;
}

.item-name {
  font-weight: 600;
  font-size: 1rem;
}

.item-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
  font-size: 0.8rem;
}

.item-stat {
  text-align: center;
}

.item-stat-label {
  color: #888;
  font-size: 0.7rem;
  text-transform: uppercase;
}

.item-stat-value {
  font-weight: 600;
}

.item-stat-value.weight { color: #e67e22; }
.item-stat-value.value { color: #27ae60; }
.item-stat-value.efficiency { color: #3498db; }

/* Status badge */
.item-status {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.7rem;
  font-weight: 600;
}

.item-status.in-bag {
  background: #28a745;
  color: white;
}

/* Knapsack State */
.capacity-bar-container {
  margin-bottom: 1rem;
}

.capacity-label {
  display: flex;
  justify-content: space-between;
  margin-bottom: 0.5rem;
  font-size: 0.9rem;
  color: #555;
}

.capacity-bar {
  height: 20px;
  background: #e9ecef;
  border-radius: 10px;
  overflow: hidden;
}

.capacity-fill {
  height: 100%;
  background: linear-gradient(90deg, #28a745, #20c997);
  border-radius: 10px;
  transition: width 0.3s ease, background 0.3s ease;
  width: 0%;
}

.capacity-fill.warning {
  background: linear-gradient(90deg, #ffc107, #fd7e14);
}

.capacity-fill.full {
  background: linear-gradient(90deg, #dc3545, #c82333);
}

.capacity-fill.over {
  background: linear-gradient(90deg, #dc3545, #721c24);
  animation: pulse-over 0.8s ease-in-out infinite;
}

@keyframes pulse-over {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.7; }
}

/* Over capacity warning */
.over-capacity-warning {
  display: none;
  background: linear-gradient(135deg, #f8d7da 0%, #f5c6cb 100%);
  border: 2px solid #dc3545;
  border-radius: 8px;
  padding: 0.75rem 1rem;
  margin-top: 0.75rem;
  font-size: 0.9rem;
  font-weight: 600;
  color: #721c24;
  text-align: center;
}

.stats-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin-bottom: 1rem;
}

.stat-box {
  text-align: center;
  padding: 0.75rem;
  border-radius: 8px;
  background: #f8f9fa;
}

.stat-value {
  font-size: 1.75rem;
  font-weight: 700;
  color: #667eea;
}

.stat-label {
  font-size: 0.8rem;
  color: #666;
}

.actions {
  display: flex;
  gap: 0.75rem;
}

.btn {
  flex: 1;
  padding: 0.75rem 1rem;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-primary {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

.btn-secondary {
  background: #e9ecef;
  color: #495057;
}

.btn-secondary:hover {
  background: #dee2e6;
}

/* Optimal Section */
.optimal-section {
  background: linear-gradient(135deg, #ffecd2 0%, #fcb69f 100%);
  border: 2px dashed #e67e22;
}

.optimal-info {
  font-size: 0.95rem;
  color: #8b4513;
  line-height: 1.6;
}

/* Chart Section */
.chart-section {
  min-height: 350px;
}

.chart-container {
  height: 280px;
  position: relative;
}

.chart-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
  margin-top: 1rem;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
}

.legend-color {
  width: 16px;
  height: 16px;
  border-radius: 4px;
}

.legend-line {
  width: 20px;
  height: 0;
}

/* Analysis Section */
.analysis-content {
  font-size: 0.9rem;
  line-height: 1.6;
}

.analysis-content .placeholder {
  color: #888;
  text-align: center;
  padding: 1rem;
}

.analysis-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem;
  background: #f8f9fa;
  border-radius: 8px;
  margin-bottom: 0.5rem;
}

.analysis-item:last-child {
  margin-bottom: 0;
}

.analysis-icon {
  font-size: 1.5rem;
}

.analysis-text {
  flex: 1;
}

.analysis-text strong {
  color: #667eea;
}

.analysis-value {
  font-weight: 600;
  font-size: 1.1rem;
}

.analysis-value.positive { color: #28a745; }
.analysis-value.negative { color: #dc3545; }

/* Efficiency bars */
.efficiency-bars {
  margin-top: 1rem;
}

.efficiency-bar-item {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.5rem;
}

.efficiency-bar-label {
  width: 60px;
  font-size: 0.85rem;
  font-weight: 500;
}

.efficiency-bar-track {
  flex: 1;
  height: 20px;
  background: #e9ecef;
  border-radius: 4px;
  overflow: hidden;
}

.efficiency-bar-fill {
  height: 100%;
  border-radius: 4px;
  transition: width 0.5s ease;
}

.efficiency-bar-value {
  width: 50px;
  text-align: right;
  font-size: 0.85rem;
  font-weight: 600;
}

/* Explainer Section */
.explainer-content {
  font-size: 0.9rem;
  line-height: 1.7;
  color: #555;
}

.explainer-content p {
  margin-bottom: 0.75rem;
}

.explainer-content ul {
  margin: 0.75rem 0;
  padding-left: 1.5rem;
}

.explainer-content li {
  margin-bottom: 0.5rem;
}

.explainer-content code {
  display: block;
  background: rgba(102, 126, 234, 0.1);
  padding: 0.75rem;
  border-radius: 6px;
  font-size: 0.85rem;
  color: #5a4fba;
  margin: 0.75rem 0;
}

.explainer-content strong {
  color: #333;
}

.explainer-content em {
  color: #e67e22;
  font-style: normal;
}

/* ODE running state */
.ode-running {
  position: relative;
}

.ode-running::after {
  content: 'Simulating...';
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  background: rgba(102, 126, 234, 0.9);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: 6px;
  font-weight: 600;
}