* {
  box-sizing: border-box;
}

:root {
  --bg: #0d0d0d;
  --text: #e0e0e0;
  --text-muted: #888;
  --heading: #fff;
  --panel-bg: #1a1a1a;
  --panel-border: #2a2a2a;
  --input-bg: #252525;
  --input-border: #3a3a3a;
  --btn-bg: #3a3a3a;
  --btn-bg-hover: #4a4a4a;
  --canvas-shadow: rgba(0, 0, 0, 0.5);
}

[data-theme="light"] {
  --bg: #f5f5f5;
  --text: #333;
  --text-muted: #666;
  --heading: #111;
  --panel-bg: #fff;
  --panel-border: #ddd;
  --input-bg: #fff;
  --input-border: #ccc;
  --btn-bg: #e0e0e0;
  --btn-bg-hover: #d0d0d0;
  --canvas-shadow: rgba(0, 0, 0, 0.15);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
  background: var(--bg);
  color: var(--text);
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem;
  min-height: 100vh;
  transition: background 0.2s, color 0.2s;
}

header {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
  margin-bottom: 2rem;
}

h1 {
  font-size: 2.5rem;
  font-weight: 300;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--heading);
  margin: 0;
  text-align: center;
}

#themeBtn {
  position: absolute;
  right: 0;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0.5rem;
  opacity: 0.7;
  transition: opacity 0.2s;
}

#themeBtn:hover {
  opacity: 1;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
  margin-bottom: 1.5rem;
  padding: 1.25rem;
  background: var(--panel-bg);
  border-radius: 8px;
  border: 1px solid var(--panel-border);
  transition: background 0.2s, border-color 0.2s;
}

input[type="file"] {
  flex: 1;
  min-width: 200px;
  padding: 0.5rem;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: 6px;
  color: var(--text);
  font-size: 0.9rem;
  cursor: pointer;
  transition: background 0.2s, border-color 0.2s, color 0.2s;
}

input[type="file"]::file-selector-button {
  padding: 0.5rem 1rem;
  margin-right: 1rem;
  background: var(--btn-bg);
  border: none;
  border-radius: 4px;
  color: var(--heading);
  font-size: 0.85rem;
  cursor: pointer;
  transition: background 0.2s, color 0.2s;
}

input[type="file"]::file-selector-button:hover {
  background: var(--btn-bg-hover);
}

input[type="file"]:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

input[type="file"]:disabled::file-selector-button {
  cursor: not-allowed;
}

button {
  padding: 0.6rem 1.25rem;
  font-size: 0.9rem;
  font-weight: 500;
  border: none;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s ease;
}

#startBtn {
  background: #22c55e;
  color: #000;
}

#startBtn:hover:not(:disabled) {
  background: #16a34a;
}

#stopBtn {
  background: #ef4444;
  color: #fff;
}

#stopBtn:hover:not(:disabled) {
  background: #dc2626;
}

#resetBtn {
  background: #3b82f6;
  color: #fff;
}

#resetBtn:hover:not(:disabled) {
  background: #2563eb;
}

button:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

canvas {
  display: block;
  width: 100%;
  height: auto;
  margin-bottom: 1.5rem;
  border-radius: 8px;
  box-shadow: 0 4px 24px var(--canvas-shadow);
  background: #000;
  image-rendering: pixelated;
}

.stats {
  display: flex;
  justify-content: center;
  gap: 2rem;
  padding: 1rem 1.5rem;
  background: var(--panel-bg);
  border-radius: 8px;
  border: 1px solid var(--panel-border);
  font-size: 0.9rem;
  color: var(--text-muted);
  transition: background 0.2s, border-color 0.2s;
}

.stats span {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.stats strong {
  color: var(--heading);
  font-weight: 600;
}

#iterations {
  color: #f59e0b;
}

#fitness {
  color: #22c55e;
}

#status {
  color: #3b82f6;
}

@media (max-width: 600px) {
  body {
    padding: 1rem;
  }

  h1 {
    font-size: 1.75rem;
  }

  .controls {
    flex-direction: column;
  }

  input[type="file"] {
    width: 100%;
  }

  .controls button {
    width: 100%;
  }

  .stats {
    flex-direction: column;
    gap: 0.75rem;
    text-align: center;
  }
}