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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: #f5f5f5;
  color: #333;
  min-height: 100vh;
}

.container {
  max-width: 640px;
  margin: 0 auto;
  padding: 20px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header {
  text-align: center;
  padding: 40px 0 30px;
}

header h1 {
  font-size: 2rem;
  color: #1a1a2e;
  letter-spacing: 2px;
}

.subtitle {
  font-size: 1.1rem;
  color: #666;
  margin-top: 8px;
}

main {
  display: flex;
  flex-direction: column;
  gap: 20px;
  flex: 1;
}

.step {
  background: #fff;
  border-radius: 12px;
  padding: 30px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

.step h2 {
  font-size: 1.2rem;
  margin-bottom: 20px;
  color: #1a1a2e;
}

.amounts {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}

.amount-btn {
  padding: 18px 12px;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  background: #fff;
  font-size: 1.1rem;
  font-weight: 600;
  color: #333;
  cursor: pointer;
  transition: all 0.2s;
  text-align: center;
}

.amount-btn:hover {
  border-color: #1a1a2e;
  background: #f8f8ff;
}

.amount-btn.selected {
  border-color: #1a1a2e;
  background: #1a1a2e;
  color: #fff;
}

.amount-btn.sold-out {
  opacity: 0.4;
  cursor: not-allowed;
  text-decoration: line-through;
}

.amount-btn .avail {
  display: block;
  font-size: 0.75rem;
  font-weight: 400;
  color: #999;
  margin-top: 4px;
}

.amount-btn.selected .avail {
  color: #ccc;
}

.field {
  margin-bottom: 16px;
}

.field label {
  display: block;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 6px;
  color: #555;
}

.field input {
  width: 100%;
  padding: 12px 14px;
  border: 2px solid #e0e0e0;
  border-radius: 8px;
  font-size: 1rem;
  transition: border-color 0.2s;
  outline: none;
}

.field input:focus {
  border-color: #1a1a2e;
}

.summary {
  text-align: center;
  padding: 16px;
  margin: 20px 0;
  background: #f8f8ff;
  border-radius: 8px;
  font-size: 1.1rem;
}

.btn-pay {
  width: 100%;
  padding: 16px;
  background: #1a1a2e;
  color: #fff;
  border: none;
  border-radius: 10px;
  font-size: 1.1rem;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.2s;
}

.btn-pay:hover {
  background: #2d2d4e;
}

.btn-pay:disabled {
  background: #999;
  cursor: not-allowed;
}

.btn-secondary {
  padding: 12px 24px;
  background: #fff;
  color: #1a1a2e;
  border: 2px solid #1a1a2e;
  border-radius: 10px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}

.btn-secondary:hover {
  background: #1a1a2e;
  color: #fff;
}

.success-icon {
  text-align: center;
  font-size: 3rem;
  color: #4caf50;
  margin-bottom: 16px;
}

.error-icon {
  text-align: center;
  font-size: 3rem;
  color: #f44336;
  margin-bottom: 16px;
}

#step-success, #step-error {
  text-align: center;
}

#step-success p, #step-error p {
  margin: 12px 0 24px;
  color: #666;
}

footer {
  text-align: center;
  padding: 30px 0 20px;
  color: #999;
  font-size: 0.85rem;
}

@media (max-width: 480px) {
  .amounts {
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
  }
  .amount-btn {
    padding: 14px 8px;
    font-size: 1rem;
  }
  header h1 {
    font-size: 1.6rem;
  }
  .step {
    padding: 20px;
  }
}