Hey there,
sorry I didn't check on any answers earlier, so.
Currently the minimal zoom is based on your entities size, so you can just play all the way zoomed in - it will automatically zoom out, if needed. I didn't want to forbid zooming all the way out, because the world just looks great like that in my opinion.
I know the game is hard at start and levels tend to become easy too fast, but the current ones are meant to be easy. It is possible to add new types of entities, which fly around randomly, or even have some basic intelligence, competing with the player. Same applies to worlds - objectives can be added easily. One could theoretically add triggers too.
Entities size is based on surface (which is "mass"), not on radius, so there already is a square. I have tried volume - 3d - using a sphere instead of a circle, but there wasn't enough size difference for my taste. I tried to keep levels short, so I didn't want to use extreme mass difference either.
Some more information:
From now on this game shall be licensed under err..
GPL 2.0!
Feel free to add to it, port it and oh - fix all the bugs!