You know all those jokes about building a version of Minecraft inside Minecraft? Well...
YouTuber SethBling has plenty of cool Minecraft videos on his channel. He's made a Katamari Data Pack, which lets him roll up animals into a ball. He's made what is essentially a 3D printer that creates Polaroids.
Perhaps most impressively, he made an Atari 2600 emulator within Minecraft back in 2016. And now, he's made...well, Minecraft. But in 2D.
When SethBling opens the chest, the squares inside it are now populated by different Minecraft elements that ultimately make up a playable 2D version of the full game, complete with a playable Steve would can move and jump through it.
When Seth clicks on a 'tree' enough times, it gets added to his inventory, which is a whole separate screen. He's built a house in there and everything. Early on he encounters a 'lake' (the blocks are blue to indicate water) and needs to use wood he has collected from trees to make a crossing. It's wild.
Obviously it's fairly restricted, but it's also pretty damn impressive, and SethBling takes time to go over how he did it in the video. There's a download link included on the YouTube page if you want to check it out for yourself. It'll only work with Minecraft on PC, of course.