* { box-sizing: border-box; margin: 0; padding: 0; font-family: Inter, system-ui, -apple-system, sans-serif; }
body { background: #f5f7fa; color: #111; }
.header { background: #0f172a; color: white; padding: 16px 24px; display: flex; justify-content: space-between; align-items: center; }
.logo { font-size: 1.4rem; font-weight: 700; letter-spacing: -0.5px; }
.badge { background: #ef4444; color: white; font-size: 0.75rem; padding: 4px 10px; border-radius: 999px; font-weight: 600; }
.container { max-width: 1100px; margin: 0 auto; padding: 32px 16px; }
h1 { font-size: 1.8rem; margin-bottom: 8px; }
.sub { color: #64748b; margin-bottom: 28px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 16px; }
.card-tile {
  border-radius: 12px; padding: 28px 12px; text-align: center; cursor: pointer;
  font-weight: 800; font-size: 1.15rem; color: white; text-shadow: 0 1px 2px rgba(0,0,0,.3);
  transition: transform .15s, box-shadow .15s; position: relative; overflow: hidden;
  min-height: 110px; display: flex; flex-direction: column; justify-content: center;
}
.card-tile:hover { transform: translateY(-4px); box-shadow: 0 12px 24px rgba(0,0,0,.15); }
.discount { position: absolute; top: 8px; right: 8px; background: #fff; color: #ef4444;
  font-size: 0.7rem; font-weight: 800; padding: 3px 7px; border-radius: 6px; }
.step { display: none; }
.step.active { display: block; }
.amounts { display: flex; flex-wrap: wrap; gap: 10px; margin: 20px 0; }
.amt-btn {
  padding: 12px 22px; border: 2px solid #e2e8f0; border-radius: 10px; background: white;
  font-weight: 600; cursor: pointer; font-size: 1rem;
}
.amt-btn.selected, .amt-btn:hover { border-color: #0f172a; background: #0f172a; color: white; }
.form-card {
  background: white; border-radius: 16px; padding: 28px; box-shadow: 0 4px 20px rgba(0,0,0,.06);
  max-width: 480px; margin: 0 auto;
}
label { display: block; font-size: 0.85rem; font-weight: 600; margin: 14px 0 6px; color: #334155; }
input, select {
  width: 100%; padding: 12px 14px; border: 1.5px solid #e2e8f0; border-radius: 10px;
  font-size: 1rem; outline: none;
}
input:focus { border-color: #0f172a; }
.row { display: flex; gap: 12px; }
.row > * { flex: 1; }
.pay-btn {
  width: 100%; margin-top: 24px; padding: 16px; background: #0f172a; color: white;
  border: none; border-radius: 12px; font-size: 1.05rem; font-weight: 700; cursor: pointer;
}
.pay-btn:disabled { opacity: .6; cursor: not-allowed; }
.error-box {
  background: #fef2f2; border: 1px solid #fecaca; color: #b91c1c; padding: 20px;
  border-radius: 12px; text-align: center; margin-top: 20px; display: none;
}
.back { color: #64748b; cursor: pointer; font-size: 0.9rem; margin-bottom: 16px; display: inline-block; }
.summary { background: #f8fafc; padding: 14px; border-radius: 10px; margin-bottom: 18px; font-size: 0.95rem; }
#amexField { display: none; }
#cardError { font-weight: 600; }
input.invalid { border-color: #ef4444 !important; }
input.valid { border-color: #16a34a !important; }