body {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
  background: #f0f0f0;
  text-align: center;
}

#main {
  max-width: 500px;
  margin: auto;
  padding: 20px;
  background: white;
  margin-top: 50px;
  border-radius: 10px;
  box-shadow: 0 0 10px rgba(0,0,0,0.1);
}

button {
  padding: 10px 20px;
  margin: 10px;
  background: #007bff;
  color: white;
  border: none;
  border-radius: 5px;
  font-size: 16px;
}

button:hover {
  background: #0056b3;
}

input {
  padding: 10px;
  font-size: 16px;
  width: 80%;
  margin: 10px auto;
  display: block;
  border-radius: 5px;
  border: 1px solid #ccc;
}

#buzzer {
  width: 200px;
  height: auto;
  cursor: pointer;
  margin: 20px auto;
}

@media (max-width: 600px) {
  #main {
    margin-top: 20px;
    width: 90%;
    padding: 10px;
  }

  button {
    width: 90%;
    font-size: 18px;
  }

  input {
    width: 90%;
  }

  #buzzer {
    width: 150px;
  }
}

/* Buzzer: Kreis, zentriert, mit Übergang */
#buzzer {
  width: 200px;
  height: 200px;
  border-radius: 50%;
  margin: 20px auto;
  cursor: pointer;
  transition: background-color 0.3s ease;
}

/* Off-Zustand: rot */
.buzzer-off {
  background-color: green;
}

/* On-Zustand: grün */
.buzzer-on {
  background-color: red;
}