body {
  font-family: Arial;
  background: #f5f5f5;
  text-align: center;
}

.container {
  margin-top: 100px;
}

button {
  padding: 12px 25px;
  font-size: 16px;
  cursor: pointer;
}

#loading {
  width: 300px;
  height: 8px;
  background: #ddd;
  margin: 20px auto;
  border-radius: 5px;
  overflow: hidden;
}

.bar {
  width: 0%;
  height: 100%;
  background: #4caf50;
  animation: loading 2s linear infinite;
}

.hidden {
  display: none;
}

@keyframes loading {
  0% { width: 0%; }
  50% { width: 70%; }
  100% { width: 100%; }
}

pre {
  text-align: left;
  background: #000;
  color: #0f0;
  padding: 10px;
  width: 60%;
  margin: 20px auto;
}