body {
  margin: 0;
  font-family: 'Segoe UI', sans-serif;
  background-color: #0d0d0d;
  color: #f1f1f1;
}
.container {
  max-width: 700px;
  margin: auto;
  padding: 30px;
  text-align: center;
}
h1 {
  color: #00ffaa;
}
.controls {
  margin: 20px 0;
}
select, button {
  padding: 10px;
  margin: 5px;
  border-radius: 5px;
  border: none;
}
button {
  background-color: #00ffaa;
  color: #000;
  cursor: pointer;
  font-weight: bold;
}
.signal-box {
  background: #1f1f1f;
  padding: 20px;
  border-radius: 10px;
  margin-top: 20px;
  font-size: 18px;
}
.timer-box {
  margin-top: 10px;
  color: #999;
}