OneBlock is EXACTLY what it sounds like. You start out with one block. There are 23 challenges (3 of them are for 1.9; they're optional.) If you were wondering, the one block that you start with, is a chest. Yes. A chest. Where else would you get your items?
If you are recording while you are playing, give a shout out to Donkey_101, the only guy who was in this. Yes, I am lonley. Have a great day!