Drawing, erasing, and grid lines!

I’ve added quite a few things on this update, though it looks largely the same when you start it up. First up is the new grid lines. They are off by default, but they work even down to 1px, though you can’t see the grid for the gridlines at that resolution, but you can do it. They are a light grey color by default, but you can change it.

The second major change is that you can now draw on the grid! Also turned off by default, you can enable it and then draw and erase. Erasing works on anything, including sand, ants, and turmites, so be careful.

Finally there were some performance increases under the hood, so that whenever you delete ants they are gone and not still running in the background.