I have implemented a while ago an Android version (https://play.google.com/store/apps/details?hl=en-gb&id=com.ovaludi.nothree.android https://play.google.com/st

I have implemented a while ago an Android version (https://play.google.com/store/apps/details?hl=en-gb&id=com.ovaludi.nothree.android https://play.google.com/store/apps/details?hl=en-gb&id=com.o...). By far, the most interesting part is automatically generating the levels by difficulty. In my implementation, I first generate a full puzzle and then start removing pieces one by one, as long as the part just removed can be logically deduced. The only difference between easy/medium/hard is the amount of work performed in the logical deduction: one step for easy, two steps for medium and three for hard.