body {
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
  background: #222;
  color: #eee;
  height: 100vh;
  margin: 0;
}

h1 {
  font-weight: 600;
  font-size: 20px;
  margin-top: 16px;
}

#oscilloscope {
  background-color: #000;
  border: 5px solid #4caf50;
  border-radius: 15px;
  display: block;
  margin-top: 12px;
  box-shadow: 0 0 12px rgba(0,0,0,0.5) inset;
}

#controls {
  margin-top: 12px;
  text-align: center;
}

#controls label {
  font-size: 1.1em;
}

#controls input[type="range"] {
  width: 380px;
  margin-top: 8px;
}

#controls button {
  margin-left: 10px;
  padding: 8px 15px;
  font-size: 1em;
  cursor: pointer;
  border: none;
  border-radius: 6px;
  background: #4caf50;
  color: white;
}

#controls button:hover {
  background: #45a049;
}

#message {
  margin-top: 10px;
  font-size: 1.05em;
  height: 1.4em;
}