body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  font-family: sans-serif;
  background: #f9f9f9;
}

#c-test-btn {
  padding: 1rem 2rem;
  font-size: 1.2rem;
  cursor: pointer;
  border: 1px solid #333;
  background: #fff;
}