body {
  margin: 0;
  background-color: #000;
  color: #fff;
  font-family: Arial, sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
}

h1 {
  margin: 1rem 0;
}

#container {
  width: 100vw;
  height: 60vh;
}

#control-panel {
  width: 90vw;
  max-width: 600px;
  margin: 1rem 0 3rem;
  background: #111;
  padding: 1rem;
  border-radius: 8px;
}

#control-panel h2 {
  margin-top: 0;
}

.slider-wrapper {
  display: flex;
  align-items: center;
  margin-bottom: 0.5rem;
}

.slider-wrapper label {
  flex: 1 0 100px;
  font-size: 14px;
}

.slider-wrapper input[type="range"] {
  flex: 1 1 auto;
}

#container {
  width: 100vw;
  height: 60vh;
  position: relative;
  z-index: 0;
}

#control-panel {
  position: relative;
  z-index: 10;
  background: #111;
  /* make sure it’s below the canvas or nicely spaced */
  margin-top: 1rem;
}