Anybody who enjoyed Sprout will probably like Sphere. If you get stuck, like we did, you can go here and read the instructions posted by mykos. It's hard to read it without getting more information than you might want, though, so you may want to ask someone else to read it and give you a hint.

That game led us to MOTAS, another good one.

Then there's Frostbite. We haven't tried that one yet but it looks like fun.