*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

body {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #fff;
}

#buy-btn {
  display: inline-block;
  padding: 1rem 2.5rem;
  font-size: 1.1rem;
  text-decoration: none;
  cursor: pointer;
}

.container {
  text-align: center;
  padding: 2rem;
}

.checkmark {
  font-size: 4rem;
  margin-bottom: 1rem;
  color: #4ade80;
}