I recently had an idea for a challenge I could do. The basics are that I start a customized world with only desert biome (of course rivers spawn cuz Mojang, but I basically just ignore them). Villages are turned off and dirt has been made rare on the order of diamonds (though it can be found at all depths). I have spawned with a bonus chest. The rules I'm playing with include: I can't use any trees, so no farming them. I can't use any surface dirt or grass I find, only what I can find underground (that includes tallgrass).
Immediately, as I started the world I ran into the problem of food. The bonus chest had provided me with enough wood to get a crafting table, and included some tools to get me started, but contained very little sustenance. There was a Desert temple very close to me, which was lucky, but of course, those generally don't have food, only rotten flesh. Wood so far hasn't been a huge issue, since I can get sticks from dead bushes, but those won't last forever.
The only way I could think of to get food was to venture into the caves and hope I got a carrot or potato from a zombie. If I got a carrot, I could start breeding the rabbits (being the only farm animal to spawn in deserts). I explored for a long time, eventually getting fully geared in iron armor and finding two blocks of dirt. Then, I found the spawner. Unfortunately, it didn't have any beetroot seeds in the chest, but it did have some bread. I set up a very crude murder hole style mob grinder around the spawner so that I could farm rotten flesh. After farming it for a bit I did manage to get a carrot, and set up a tiny, two block farm on the surface. In order for it to be effective, I'm going to have to use a lot of bonemeal. I managed to create a tiny pen and lure some rabbits in as well.
That was as far as I got today, but I'm already liking the feel of the challenge. It still feels like I'm playing Minecraft, unlike some I've played, yet it is just difficult and different enough. It makes you think in new ways, since you really have to be creative on how you get your food and wood.
My goals for the future will be to find a skeleton spawner to fuel my microfarm, and also to find a mineshaft. If I can do that before my log supply runs out (I did use some for a bed), then I should be good on wood for a while. The bad thing is that even that will eventually run out. Either I'll have to keep venturing further and further to find wood, or it will eventually force me to relocate, leaving my old base behind.