body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  background: linear-gradient(to bottom right, #6a11cb, #2575fc);
  color: white;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

.hidden {
  display: none;
}

#loginScreen, #incomingCall, #callScreen {
  text-align: center;
}

input, button {
  margin: 10px;
  padding: 10px;
  font-size: 16px;
  border: none;
  border-radius: 8px;
}

button.green {
  background-color: #4CAF50;
  color: white;
}

button.red {
  background-color: #f44336;
  color: white;
}

#callControls button {
  margin: 5px;
  padding: 10px 20px;
  font-size: 20px;
}

@media (min-width: 768px) {
  body {
    flex-direction: row;
  }
}