body {
  margin: 0;
  font-family: "Poppins", sans-serif;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;

  /* Gradient động */
  background: linear-gradient(-45deg, #1a2a6c, #b21f1f, #fdbb2d, #21d4fd);
  background-size: 400% 400%;
  animation: gradientBG 15s ease infinite;
}

@keyframes gradientBG {
  0% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
  100% { background-position: 0% 50%; }
}

.container {
  background: rgba(255, 255, 255, 0.95);
  padding: 40px;
  border-radius: 12px;
  box-shadow: 0 6px 25px rgba(0, 0, 0, 0.3);
  text-align: center;
  max-width: 600px;
  width: 100%;
}

h2 {
  font-size: 20px;
  margin-bottom: 20px;
}

input[type="email"] {
  padding: 12px;
  width: 70%;
  border-radius: 6px;
  border: 1px solid #ccc;
  font-size: 16px;
}

button {
  padding: 12px 20px;
  font-size: 16px;
  font-weight: 600;
  border: none;
  border-radius: 6px;
  background: #007bff;
  color: white;
  cursor: pointer;
}

button:hover {
  background: #0056b3;
}

.error-msg {
  color: red;
  font-size: 14px;
  margin-top: 10px;
}

.box {
  margin-top: 30px;
  font-size: 16px;
  line-height: 1.6;
}