Wot you guys think of Infinifactory, for the price?
Infinifactory was a very solid buy for me when it came out. It's... kinda like his earlier free work, or like SpaceChem, but frankly it's easier. Also a lot like designing industrial systems in Minecraft modpacks like FTB.
It's still hard, but I'm bad at puzzle games and never got particularly frustrated. Couldn't get far in SpaceChem (as much as I enjoyed it), yet got through this and felt great.
Example of his free stuff, though obviously his interface design is *far* improved now:
http://www.zachtronics.com/the-codex-of-alchemical-engineering/I want to go back and play the new free missions he added to Infinifactory, sometime.
Edit: One thing about the difficulty is that a lot of it is optional. There's no reward for having a more efficient system, or using less pieces (technically, smaller footprint). But it tells you, and that was enough to where I tried to design system which worked as fast as possible. There's a thrill of seeing the next piece slide in juuuust after the previous moves out of the way.
Or in having a system that gets the job done fast, but spews extra pieces off the map or into a growing mound of detritus.