/* Default background for light mode */
body {
  background-color: #f7f7f7;
  color: #222;
  transition: background-color 0.3s ease, color 0.3s ease;
}

/* Dark mode by system preference */
@media (prefers-color-scheme: dark) {
  body {
    background-color: #121212;
    color: #eee;
  }
}
body.light {
  background-color: #f7f7f7;
  color: #222;
}

body.dark {
  background-color: #121212;
  color: #eee;
}

:root {
  --color-bg-light: #e6f2ff;
  --color-bg-dark: #0a1a2b;
  --color-text-light: #033649;
  --color-text-dark: #a9c3e0;
  --color-primary-light: #4da6ff;
  --color-primary-dark: #3399ff;
  --color-primary-hover-light: #3399ff;
  --color-primary-hover-dark: #4da6ff;
  --color-control-bg-light: #ffffffcc;
  --color-control-bg-dark: #1a2a4acc;
}

/* Light mode (default) */
body {
  margin: 0; padding: 0; height: 100%;
  background: linear-gradient(to bottom, var(--color-bg-light), #b3d1ff);
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  color: var(--color-text-light);
  display: flex;
  flex-direction: column;
  align-items: center;
  transition: background 0.5s, color 0.5s;
  position: relative;
}
h1 {
  margin-top: 1rem;
  font-weight: 300;
  text-align: center;
}
#intro {
  max-width: 720px;
  width: 95%;
  margin-bottom: 1.5rem;
  font-size: 1.1rem;
  line-height: 1.5;
  text-align: center;
  color: var(--color-text-light);
  transition: color 0.5s;
}
#playPauseBtn {
  margin: 1rem 0 2rem;
  padding: 1rem 2rem;
  font-size: 1.25rem;
  border: none;
  border-radius: 8px;
  background-color: var(--color-primary-light);
  color: white;
  cursor: pointer;
  transition: background-color 0.3s;
}
#playPauseBtn:hover {
  background-color: var(--color-primary-hover-light);
}

#controls {
  width: 95%;
  max-width: 720px;
  background-color: var(--color-control-bg-light);
  border-radius: 12px;
  padding: 1.5rem 2rem;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: 1.2rem;
  margin-bottom: 2rem;
  transition: background-color 0.5s;
}
.sound-control {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.sound-control label {
  flex: 1 0 140px;
  font-weight: 600;
  user-select: none;
}
.sound-control input[type="range"] {
  flex: 1 1 auto;
  margin-left: 1rem;
  cursor: pointer;
}
#masterVolumeContainer {
  margin-bottom: 1rem;
  width: 100%;
}
#presets {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 1rem;
}
.preset-btn {
  flex: 1 1 calc(33% - 10px);
  background-color: var(--color-primary-light);
  color: white;
  border: none;
  border-radius: 6px;
  padding: 0.5rem 0;
  cursor: pointer;
  user-select: none;
  font-weight: 600;
  transition: background-color 0.3s;
}
.preset-btn.selected {
  background-color: #2673cc;
}
.preset-btn:hover:not(.selected) {
  background-color: var(--color-primary-hover-light);
}
canvas {
  position: fixed;
  top: 0; left: 0;
  z-index: -1;
  transition: background-color 0.5s;
}

/* Dark mode */
body.dark {
  background: linear-gradient(to bottom, var(--color-bg-dark), #041323);
  color: var(--color-text-dark);
}
body.dark #intro {
  color: var(--color-text-dark);
}
body.dark #controls {
  background-color: var(--color-control-bg-dark);
}
body.dark #playPauseBtn {
  background-color: var(--color-primary-dark);
  color: white;
}
body.dark #playPauseBtn:hover {
  background-color: var(--color-primary-hover-dark);
}
body.dark .preset-btn {
  background-color: var(--color-primary-dark);
}
body.dark .preset-btn.selected {
  background-color: #1a3b6e;
}
body.dark .preset-btn:hover:not(.selected) {
  background-color: var(--color-primary-hover-dark);
}

/* Dark/light toggle switch in top-right */
#modeToggleWrapper {
  position: fixed;
  top: 1rem;
  right: 1rem;
  z-index: 10;
  user-select: none;
}
.switch {
  position: relative;
  display: inline-block;
  width: 52px;
  height: 28px;
}
.switch input {
  opacity: 0;
  width: 0; height: 0;
}
.slider {
  position: absolute;
  cursor: pointer;
  top: 0; left: 0; right: 0; bottom: 0;
  background-color: #ccc;
  transition: 0.4s;
  border-radius: 14px;
}
.slider:before {
  position: absolute;
  content: "";
  height: 22px;
  width: 22px;
  left: 3px;
  bottom: 3px;
  background-color: white;
  transition: 0.4s;
  border-radius: 50%;
}
input:checked + .slider {
  background-color: var(--color-primary-light);
}
input:checked + .slider:before {
  transform: translateX(24px);
}
body.dark input:checked + .slider {
  background-color: var(--color-primary-dark);
}

#startOverlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(0, 0, 0, 0.75);
  color: #eee;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.8rem;
  text-align: center;
  cursor: pointer;
  z-index: 9999;
  user-select: none;
}

#startMessage {
  padding: 20px 40px;
  background: rgba(30, 30, 30, 0.85);
  border-radius: 12px;
  box-shadow: 0 0 15px rgba(0,0,0,0.6);
  max-width: 90vw;
  font-weight: 600;
}

.sound-control {
  margin: 10px 0;
  display: flex;
  align-items: center;
  gap: 12px;
}

.sound-control label {
  flex: 0 0 120px;
  font-weight: 600;
  user-select: none;
}

.sound-control input[type="range"] {
  flex: 1;
  height: 6px;
  border-radius: 4px;
  cursor: pointer;
}