:root {
  --bg: #0f1729;
  --surface: #ffffff;
  --surface-muted: #f8fafc;
  --text: #1e293b;
  --text-muted: #64748b;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --border: #e2e8f0;
  --error: #dc2626;
  --success: #16a34a;
  --success-bright: #22c55e;
  --success-hover: #16a34a;
  --overlay: rgba(15, 23, 41, 0.75);
  --payment-bg: #1a2234;
  --payment-details-bg: #252d3d;
  --payment-text: #e2e8f0;
  --payment-muted: #94a3b8;
  --radius: 12px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.12);
  --transition: 0.25s ease;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
}

.app {
  max-width: 560px;
  margin: 0 auto;
  padding: 2rem 1.25rem 3rem;
}

.header {
  text-align: center;
  margin-bottom: 2rem;
}

.header h1 {
  color: var(--surface);
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.subtitle {
  color: #94a3b8;
  font-size: 0.95rem;
}

.step {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 1.75rem;
  box-shadow: var(--shadow);
  transition: opacity var(--transition);
}

.step.hidden {
  display: none;
}

.step.active {
  display: block;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

.step-title {
  font-size: 1.25rem;
  margin-bottom: 1.25rem;
  color: var(--text);
}

/* Card gallery */
.card-gallery {
  display: flex;
  gap: 1rem;
  overflow-x: auto;
  padding-bottom: 0.5rem;
  margin-bottom: 0.5rem;
  scroll-snap-type: x mandatory;
  -webkit-overflow-scrolling: touch;
}

.card-option {
  flex: 0 0 auto;
  background: none;
  border: 3px solid transparent;
  border-radius: var(--radius);
  padding: 0.5rem;
  cursor: pointer;
  transition: border-color var(--transition), transform var(--transition);
  scroll-snap-align: center;
}

.card-option img {
  display: block;
  width: 200px;
  height: auto;
  border-radius: 8px;
  pointer-events: none;
}

.card-option .card-label {
  display: block;
  text-align: center;
  margin-top: 0.5rem;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-muted);
}

.card-option .card-price {
  display: block;
  text-align: center;
  margin-top: 0.25rem;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--primary);
}

.card-option.selected .card-price {
  color: var(--primary-hover);
}

.card-option:hover {
  transform: translateY(-2px);
}

.card-option.selected {
  border-color: var(--primary);
}

.card-option.selected .card-label {
  color: var(--primary);
}

.card-option:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

/* Form */
.form {
  margin-top: 1.5rem;
}

.field {
  margin-bottom: 1.25rem;
}

.field label {
  display: block;
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 0.375rem;
  color: var(--text);
}

.field input,
.field select {
  width: 100%;
  padding: 0.75rem 1rem;
  font-size: 1rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  transition: border-color var(--transition);
}

.field input:focus,
.field select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.error {
  color: var(--error);
  font-size: 0.8125rem;
  margin-top: 0.25rem;
  min-height: 1.25rem;
}

#card-error {
  text-align: center;
  margin-bottom: 0.5rem;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.875rem 1.5rem;
  font-size: 1rem;
  font-weight: 600;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: background var(--transition), transform 0.1s ease;
}

.btn:active {
  transform: scale(0.98);
}

.btn-primary {
  width: 100%;
  background: var(--primary);
  color: var(--surface);
}

.btn-primary:hover {
  background: var(--primary-hover);
}

.btn-primary:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.btn-secondary {
  background: var(--surface-muted);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--border);
}

.btn-group {
  display: flex;
  gap: 0.75rem;
  margin-top: 0.5rem;
}

.btn-group .btn {
  flex: 1;
}

/* Summary */
.summary {
  background: var(--surface-muted);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
}

.summary-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
}

.summary-row:last-child {
  border-bottom: none;
}

.summary-label {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.summary-value {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text);
}

/* Success */
.success-content {
  text-align: center;
  padding: 1rem 0;
}

.success-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 1.25rem;
  background: var(--success);
  color: var(--surface);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  font-weight: bold;
}

.success-content h2 {
  margin-bottom: 0.75rem;
}

.success-content p {
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

/* Loader */
.loader-overlay {
  position: fixed;
  inset: 0;
  background: var(--overlay);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1100;
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition), visibility var(--transition);
}

.loader-overlay.visible {
  opacity: 1;
  visibility: visible;
}

.loader-content {
  text-align: center;
  color: var(--surface);
}

.loader-content p {
  margin-top: 1rem;
  font-size: 1rem;
  font-weight: 500;
}

.spinner {
  width: 48px;
  height: 48px;
  margin: 0 auto;
  border: 4px solid rgba(255, 255, 255, 0.25);
  border-top-color: var(--surface);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

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

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: var(--overlay);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1001;
  padding: 1.25rem;
  animation: fadeIn 0.2s ease;
}

.modal-overlay.hidden {
  display: none;
}

.modal {
  background: var(--surface);
  border-radius: var(--radius);
  padding: 2rem 1.75rem;
  max-width: 400px;
  width: 100%;
  position: relative;
  box-shadow: var(--shadow);
  animation: scaleIn 0.25s ease;
}

.modal-verify {
  max-width: 440px;
}

.verify-form {
  margin-top: 0;
}

.verify-form .field input[type="file"] {
  padding: 0.5rem;
  font-size: 0.875rem;
}

.file-preview {
  margin-top: 0.75rem;
  border-radius: 8px;
  overflow: hidden;
  border: 1px solid var(--border);
}

.file-preview.hidden {
  display: none;
}

.file-preview img {
  display: block;
  max-width: 100%;
  max-height: 160px;
  margin: 0 auto;
  object-fit: contain;
}

.verify-form .btn-primary {
  width: 100%;
  margin-top: 0.25rem;
}

.verify-form .btn-primary:disabled {
  opacity: 0.65;
  cursor: not-allowed;
}

@keyframes scaleIn {
  from { opacity: 0; transform: scale(0.95); }
  to { opacity: 1; transform: scale(1); }
}

.modal-close {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: none;
  border: none;
  font-size: 1.5rem;
  line-height: 1;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.25rem;
  border-radius: 4px;
}

.modal-close:hover {
  color: var(--text);
}

.modal-close:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
}

.modal h2 {
  font-size: 1.25rem;
  text-align: center;
  margin-bottom: 0.25rem;
}

.modal-subtitle {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.875rem;
  margin-bottom: 1.75rem;
}

.crypto-options {
  display: flex;
  justify-content: center;
  gap: 2.5rem;
}

.crypto-option {
  background: none;
  border: none;
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  padding: 0.5rem;
  border-radius: var(--radius);
  transition: transform var(--transition);
}

.crypto-option:hover {
  transform: scale(1.05);
}

.crypto-option:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 4px;
}

.crypto-circle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 80px;
  height: 80px;
  border-radius: 50%;
  overflow: hidden;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.15);
  transition: box-shadow var(--transition);
}

.crypto-option:hover .crypto-circle {
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.2);
}

.crypto-circle img {
  width: 80px;
  height: 80px;
  display: block;
}

.crypto-label {
  font-size: 0.9375rem;
  font-weight: 600;
  color: var(--text);
}

/* Payment step */
.payment-step {
  background: var(--payment-bg);
  color: var(--payment-text);
  text-align: center;
  padding: 2rem 1.75rem;
}

.payment-step.hidden {
  display: none;
}

.payment-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 0.75rem;
}

.payment-instructions {
  font-size: 0.9375rem;
  color: var(--payment-muted);
  line-height: 1.6;
  margin-bottom: 1.75rem;
  max-width: 340px;
  margin-left: auto;
  margin-right: auto;
}

.payment-instructions strong {
  color: var(--payment-text);
  font-weight: 600;
}

.qr-wrapper {
  position: relative;
  display: inline-block;
  margin-bottom: 1.75rem;
}

.qr-code {
  background: #ffffff;
  border-radius: 12px;
  padding: 12px;
  display: inline-block;
  line-height: 0;
}

.qr-code img {
  display: block;
  border-radius: 4px;
}

.qr-shield {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 44px;
  height: 44px;
  background: #ffffff;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #1a2234;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
  pointer-events: none;
}

.payment-details {
  background: var(--payment-details-bg);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1.5rem;
  text-align: center;
}

.payment-detail {
  font-size: 0.9375rem;
  color: var(--payment-text);
  margin-bottom: 0.625rem;
}

.payment-detail strong {
  font-weight: 600;
}

.payment-detail-label {
  font-size: 0.875rem;
  color: var(--payment-muted);
  margin-top: 1rem;
  margin-bottom: 0.5rem;
}

.wallet-address {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 0 auto 1rem;
  border-radius: 8px;
}

.btn-copy {
  background: var(--primary);
  color: #ffffff;
  padding: 0.625rem 1.5rem;
  font-size: 0.875rem;
  border-radius: 8px;
  width: auto;
}

.btn-copy:hover {
  background: var(--primary-hover);
}

.copy-feedback {
  font-size: 0.8125rem;
  color: var(--success-bright);
  margin-top: 0.5rem;
}

.copy-feedback.hidden {
  display: none;
}

.btn-paid {
  width: 100%;
  background: var(--success-bright);
  color: #ffffff;
  padding: 1rem 1.5rem;
  font-size: 1rem;
  font-weight: 600;
  border-radius: 10px;
  margin-bottom: 0.75rem;
}

.btn-paid:hover {
  background: var(--success-hover);
}

.btn-back-link {
  background: none;
  border: none;
  color: var(--payment-muted);
  font-size: 0.875rem;
  cursor: pointer;
  padding: 0.5rem;
  width: auto;
}

.btn-back-link:hover {
  color: var(--payment-text);
}

.app.payment-active .header {
  display: none;
}

.app.payment-active {
  max-width: 420px;
}

@media (max-width: 480px) {
  .app {
    padding: 1.5rem 1rem 2rem;
  }

  .step {
    padding: 1.25rem;
  }

  .card-option img {
    width: 160px;
  }

  .crypto-options {
    gap: 1.5rem;
  }
}