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

:root {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: #334155;
  --text-primary: #f1f5f9;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --accent-blue: #3b82f6;
  --accent-cyan: #06b6d4;
  --accent-teal: #14b8a6;
  --accent-green: #22c55e;
  --accent-yellow: #eab308;
  --border-color: #475569;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
}

.hydropower-container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 20px;
}

/* Header */
header {
  text-align: center;
  padding: 30px 20px;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 30px;
}

header h1 {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: 10px;
  background: linear-gradient(135deg, var(--accent-cyan), var(--accent-blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.subtitle {
  color: var(--text-muted);
  font-size: 1.1rem;
}

/* Main Layout */
.simulation-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 30px;
}

@media (max-width: 1024px) {
  .simulation-layout {
    grid-template-columns: 1fr;
  }
}

/* Panels */
.dam-panel,
.energy-panel {
  background: var(--bg-secondary);
  border-radius: 16px;
  padding: 20px;
  border: 1px solid var(--border-color);
}

.dam-panel h3,
.energy-panel h3 {
  font-size: 1.3rem;
  margin-bottom: 15px;
  color: var(--text-primary);
}

/* Canvas */
canvas {
  width: 100%;
  height: auto;
  border-radius: 8px;
  background: var(--bg-primary);
}

#damCanvas {
  height: 400px;
}

#energyCanvas {
  height: 250px;
}

/* Structure Legend */
.structure-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
  margin-top: 15px;
  justify-content: center;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.legend-color {
  width: 24px;
  height: 24px;
  border-radius: 4px;
}

.legend-color.reservoir {
  background: linear-gradient(180deg, #60a5fa, #0369a1);
}

.legend-color.turbine {
  background: var(--accent-teal);
}

.legend-color.generator {
  background: var(--accent-yellow);
}

/* Power Display */
.power-display {
  margin-top: 15px;
  padding: 15px;
  background: var(--bg-primary);
  border-radius: 8px;
  text-align: center;
}

.power-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.power-item span:first-child {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.power-value {
  font-size: 3rem;
  font-weight: bold;
  color: var(--accent-green);
}

.unit {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* Controls Panel */
.controls-panel {
  background: var(--bg-secondary);
  border-radius: 16px;
  padding: 25px;
  margin-bottom: 30px;
  border: 1px solid var(--border-color);
}

.controls-panel h3 {
  font-size: 1.4rem;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.controls-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  margin-bottom: 25px;
}

.control-group {
  background: var(--bg-primary);
  padding: 15px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

.control-group label {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
  font-weight: 500;
  color: var(--text-secondary);
}

.control-group input[type="range"] {
  width: 100%;
  height: 6px;
  border-radius: 3px;
  background: var(--bg-card);
  outline: none;
  -webkit-appearance: none;
}

.control-group input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent-cyan);
  cursor: pointer;
  transition: transform 0.2s;
}

.control-group input[type="range"]::-webkit-slider-thumb:hover {
  transform: scale(1.2);
}

.parameter-effect {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 10px;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.effect-icon {
  font-size: 1.1rem;
}

/* Toggle Panel */
.toggle-panel {
  background: var(--bg-primary);
  padding: 20px;
  border-radius: 10px;
  margin-bottom: 25px;
}

.toggle-panel h4 {
  font-size: 1.1rem;
  margin-bottom: 15px;
  color: var(--text-primary);
}

.toggle-options {
  display: flex;
  flex-wrap: wrap;
  gap: 15px;
}

.toggle-option {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: pointer;
  padding: 8px 15px;
  background: var(--bg-card);
  border-radius: 6px;
  transition: background 0.3s;
}

.toggle-option:hover {
  background: var(--border-color);
}

.toggle-option input[type="checkbox"] {
  width: 18px;
  height: 18px;
  accent-color: var(--accent-cyan);
}

/* Formulas Section */
.formulas-section {
  background: var(--bg-primary);
  padding: 20px;
  border-radius: 10px;
  margin-bottom: 25px;
}

.formulas-section h3 {
  font-size: 1.2rem;
  margin-bottom: 15px;
  color: var(--text-primary);
}

.formula-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.formula-item {
  padding: 12px 15px;
  background: var(--bg-card);
  border-radius: 8px;
  border-left: 3px solid var(--accent-cyan);
}

.formula-item.main {
  border-left-color: var(--accent-green);
  background: linear-gradient(135deg, rgba(6, 182, 212, 0.1), rgba(34, 197, 94, 0.1));
}

.formula-label {
  display: block;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 5px;
  font-size: 0.9rem;
}

.formula {
  font-family: 'Times New Roman', serif;
  color: var(--text-primary);
  font-size: 1.1rem;
}

.formula sub {
  font-size: 0.7em;
}

/* Data Display Panel */
.data-display-panel {
  background: var(--bg-primary);
  padding: 20px;
  border-radius: 10px;
  margin-bottom: 25px;
}

.data-display-panel h3 {
  font-size: 1.2rem;
  margin-bottom: 15px;
  color: var(--text-primary);
}

.data-readings {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 15px;
}

.data-reading {
  background: var(--bg-card);
  padding: 15px;
  border-radius: 8px;
  text-align: center;
}

.data-label {
  display: block;
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.data-value {
  font-size: 1.6rem;
  font-weight: bold;
  color: var(--accent-cyan);
}

/* Energy Diagram */
.energy-diagram {
  background: var(--bg-primary);
  padding: 20px;
  border-radius: 10px;
}

.energy-diagram h3 {
  font-size: 1.2rem;
  margin-bottom: 20px;
  color: var(--text-primary);
}

.energy-steps {
  display: flex;
  justify-content: space-around;
  align-items: center;
  gap: 15px;
  flex-wrap: wrap;
}

.energy-step {
  flex: 1;
  min-width: 120px;
}

.energy-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  padding: 20px 15px;
  border-radius: 12px;
  text-align: center;
}

.energy-box.potential {
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.2), rgba(59, 130, 246, 0.1));
  border: 2px solid var(--accent-blue);
}

.energy-box.kinetic {
  background: linear-gradient(135deg, rgba(6, 182, 212, 0.2), rgba(6, 182, 212, 0.1));
  border: 2px solid var(--accent-cyan);
}

.energy-box.mechanical {
  background: linear-gradient(135deg, rgba(20, 184, 166, 0.2), rgba(20, 184, 166, 0.1));
  border: 2px solid var(--accent-teal);
}

.energy-box.electrical {
  background: linear-gradient(135deg, rgba(34, 197, 94, 0.2), rgba(34, 197, 94, 0.1));
  border: 2px solid var(--accent-green);
}

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

.energy-box span:nth-child(2) {
  font-weight: 600;
  color: var(--text-primary);
  font-size: 0.85rem;
}

.energy-formula {
  font-family: 'Times New Roman', serif;
  font-size: 1rem;
  color: var(--text-secondary);
}

.energy-arrow {
  font-size: 1.5rem;
  color: var(--accent-green);
  font-weight: bold;
}

/* Explanation Section */
.explanation {
  background: var(--bg-secondary);
  border-radius: 16px;
  padding: 30px;
  border: 1px solid var(--border-color);
}

.explanation h2 {
  font-size: 1.8rem;
  margin-bottom: 15px;
  color: var(--text-primary);
}

.explanation h3 {
  font-size: 1.3rem;
  margin-top: 25px;
  margin-bottom: 10px;
  color: var(--accent-cyan);
}

.explanation p {
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 15px;
}

/* Responsive */
@media (max-width: 768px) {
  header h1 {
    font-size: 1.8rem;
  }

  .subtitle {
    font-size: 0.95rem;
  }

  .controls-grid {
    grid-template-columns: 1fr;
  }

  .energy-steps {
    flex-direction: column;
  }

  .energy-arrow {
    transform: rotate(90deg);
  }

  .data-readings {
    grid-template-columns: 1fr 1fr;
  }
}

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

  header {
    padding: 20px 10px;
  }

  .data-readings {
    grid-template-columns: 1fr;
  }

  .toggle-options {
    flex-direction: column;
  }

  .power-value {
    font-size: 2rem;
  }
}