```python
import math


def explode_kit(catalog, kit, want):
    """Total the base parts an order of a kit consumes."""
    if kit not in catalog:
        raise ValueError(f"the catalog does not define {kit}")
    totals = {}
    # TODO: work down from kit, turning each requirement into whole runs
    # and charging a run's parts to its sub-kits or to the base totals.
    return totals
```