:root {
  font-family: 'PingFang SC', 'Helvetica Neue', Arial, sans-serif;
  color: #111;
  background: #f5f6fa;
}

body {
  margin: 0;
}

.container {
  min-height: 100vh;
  padding: 48px 24px 96px;
}

.card {
  background: #fff;
  border-radius: 24px;
  padding: 32px;
  box-shadow: 0 30px 80px rgba(15, 15, 60, 0.08);
}

h1 {
  margin-top: 0;
  font-size: 28px;
}

.preset-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
  margin: 24px 0 32px;
}

.preset-grid button {
  border: 1px solid #d9d9e3;
  border-radius: 16px;
  padding: 16px 0;
  font-size: 16px;
  background: #fafbff;
  color: #333;
}

.preset-grid button.active {
  border-color: #1890ff;
  background: #e6f4ff;
  color: #096dd9;
}

.custom-input {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.custom-input input {
  padding: 16px;
  border-radius: 12px;
  border: 1px solid #d9d9e3;
  font-size: 18px;
}

.summary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 32px 0;
  font-size: 18px;
}

.summary strong {
  font-size: 24px;
  color: #1890ff;
}

#pay-btn {
  width: 100%;
  border: none;
  border-radius: 999px;
  padding: 18px;
  background: linear-gradient(120deg, #1890ff, #52c41a);
  color: #fff;
  font-size: 18px;
}

.hint {
  text-align: center;
  font-size: 14px;
  color: #666;
  margin-top: 32px;
}