body {
  font-family: "Poppins", sans-serif;
  background: #f8f9fa;
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

.form-container {
  background: #fff;
  padding: 2rem;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
  width: 100%;
  max-width: 400px;
}

h1 {
  text-align: center;
  color: #e63946;
  margin-bottom: 1.5rem;
}

form {
  display: flex;
  flex-direction: column;
}

label {
  margin: 0.5rem 0 0.2rem;
  font-weight: 600;
  color: #333;
}

input,
select {
  padding: 0.6rem;
  border: 1px solid #ccc;
  border-radius: 6px;
  font-size: 1rem;
}

button {
  margin-top: 1.5rem;
  padding: 0.75rem;
  background: #e63946;
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.3s;
}

button:hover {
  background: #c72f3b;
}

#message {
  margin-top: 1rem;
  text-align: center;
  font-weight: 600;
  color: green;
}
.back-btn {
  margin-top: 1rem;
  padding: 0.65rem;
  background: #6c757d;
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  width: 100%;
}

.back-btn:hover {
  background: #5a6268;
}

.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.6);
  justify-content: center;
  align-items: center;
}

/* Nội dung modal */
.modal-content {
  background: #fff;
  padding: 20px 30px;
  border-radius: 12px;
  text-align: center;
  max-width: 400px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.2);
}

.modal-content h2 {
  color: #2e7d32;
  margin-bottom: 10px;
}

.modal-content button {
  margin-top: 15px;
  padding: 10px 20px;
  border: none;
  border-radius: 8px;
  background: #2e7d32;
  color: white;
  cursor: pointer;
  font-size: 16px;
}

.modal-content button:hover {
  background: #1b5e20;
}

.loading {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(255,255,255,0.7);
  z-index: 2000;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

.spinner {
  border: 6px solid #f3f3f3;
  border-top: 6px solid #2e7d32;
  border-radius: 50%;
  width: 50px;
  height: 50px;
  animation: spin 1s linear infinite;
  margin-bottom: 10px;
}

@keyframes spin {
  0% { transform: rotate(0deg); }
  100% { transform: rotate(360deg); }
}