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

:root {
  --primary-color: #0066cc;
  --primary-hover: #0052a3;
  --success-color: #28a745;
  --error-color: #dc3545;
  --border-color: #e0e0e0;
  --text-color: #333;
  --bg-color: #f5f7fa;
  --white: #ffffff;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
}

.container {
  max-width: 800px;
  margin: 0 auto;
  padding: 20px;
}

header {
  text-align: center;
  margin-bottom: 40px;
  padding: 40px 0 20px;
}

header h1 {
  font-size: 2.5em;
  color: var(--primary-color);
  margin-bottom: 10px;
}

.subtitle {
  font-size: 1.1em;
  color: #666;
}

main {
  background: var(--white);
  border-radius: 8px;
  box-shadow: var(--shadow);
  padding: 40px;
}

h2 {
  color: var(--text-color);
  margin-bottom: 30px;
  font-size: 1.8em;
}

h3 {
  color: var(--text-color);
  margin-bottom: 20px;
  font-size: 1.3em;
  font-weight: 600;
}

.form-section {
  margin-bottom: 35px;
  padding-bottom: 35px;
  border-bottom: 1px solid var(--border-color);
}

.form-section:last-of-type {
  border-bottom: none;
}

.form-group {
  margin-bottom: 20px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

label {
  display: block;
  margin-bottom: 8px;
  font-weight: 500;
  color: var(--text-color);
}

input[type="text"],
input[type="email"],
input[type="number"],
textarea {
  width: 100%;
  padding: 12px 16px;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  font-size: 16px;
  transition: border-color 0.3s ease;
}

input:focus,
textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.1);
}

textarea {
  resize: vertical;
  font-family: inherit;
}

small {
  display: block;
  margin-top: 6px;
  color: #666;
  font-size: 0.9em;
}

.amount-input {
  position: relative;
}

.currency-symbol {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-weight: 600;
  color: var(--text-color);
}

.amount-input input {
  padding-left: 36px;
}

.card-element {
  padding: 12px 16px;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  background: var(--white);
  transition: border-color 0.3s ease;
}

.card-element:focus-within {
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(0, 102, 204, 0.1);
}

#card-errors {
  color: var(--error-color);
  margin-top: 10px;
  font-size: 0.9em;
}

.submit-button {
  width: 100%;
  padding: 16px;
  background-color: var(--primary-color);
  color: var(--white);
  border: none;
  border-radius: 6px;
  font-size: 18px;
  font-weight: 600;
  cursor: pointer;
  transition: background-color 0.3s ease;
  margin-top: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
}

.submit-button:hover:not(:disabled) {
  background-color: var(--primary-hover);
}

.submit-button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.secondary-button {
  padding: 12px 24px;
  background-color: var(--white);
  color: var(--primary-color);
  border: 2px solid var(--primary-color);
  border-radius: 6px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  margin-top: 20px;
}

.secondary-button:hover {
  background-color: var(--primary-color);
  color: var(--white);
}

.spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 3px solid rgba(255, 255, 255, 0.3);
  border-radius: 50%;
  border-top-color: var(--white);
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.hidden {
  display: none !important;
}

.payment-message {
  margin-top: 20px;
  padding: 16px;
  border-radius: 6px;
  font-size: 0.95em;
}

.payment-message.success {
  background-color: #d4edda;
  color: #155724;
  border: 1px solid #c3e6cb;
}

.payment-message.error {
  background-color: #f8d7da;
  color: #721c24;
  border: 1px solid #f5c6cb;
}

.success-container {
  text-align: center;
  padding: 60px 40px;
}

.success-icon {
  width: 80px;
  height: 80px;
  margin: 0 auto 30px;
  background-color: var(--success-color);
  color: var(--white);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 48px;
  font-weight: bold;
}

.success-container h2 {
  color: var(--success-color);
  margin-bottom: 15px;
}

.success-container p {
  color: #666;
  font-size: 1.1em;
  margin-bottom: 20px;
}

#payment-details {
  background-color: var(--bg-color);
  padding: 20px;
  border-radius: 6px;
  margin: 30px 0;
  text-align: left;
}

#payment-details p {
  margin-bottom: 10px;
  font-size: 0.95em;
}

#payment-details strong {
  color: var(--text-color);
}

footer {
  text-align: center;
  margin-top: 40px;
  padding: 20px;
  color: #666;
  font-size: 0.9em;
}

footer a {
  color: var(--primary-color);
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 768px) {
  .container {
    padding: 10px;
  }

  main {
    padding: 20px;
  }

  header h1 {
    font-size: 2em;
  }

  .form-row {
    grid-template-columns: 1fr;
  }

  h2 {
    font-size: 1.5em;
  }

  h3 {
    font-size: 1.2em;
  }
}