Make Quadtree more space-efficient #3
Description
A Quadtree is currently not as space-efficient as it could be, partially because it stores information on the cell bounds, the cell's "level", and the cell's neighbors. I think the cell bounds and cell level may be unnecessary - that might be able to be inferred by the "path" taken to reach the cell.
Including "neighbors" allows for fast computation of neighbors, at the cost of space efficiency - it's a trade-off. It might be worth reconsidering this at some point - perhaps its better to go with better space efficiency rather than fast neighbor calculations.