.coi-calculator-wrapper {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0;
}
```

**Structure:**
```
.coi-calculator-wrapper (max 1200px, centered)
  └── .coi-calculator (full width within wrapper)
      ├── .coi-header (dark)
      └── .coi-body (white)