Minecraft was created by Markus "Notch" Persson and his company Mojang which was later sold to Microsoft for 2.5 billion dollars- which explains why there has been pretty much no development on Minecraft Pi edition for more than 2 years now. Minecraft for Pi is based off of Minecraft Pocket Edition, and as such lacks creatures, adventures, night time, etc. It is unfortunately incredibly basic.
This emulator is experimental and can be installed from the experimental menu of the retropie setup script
|Double Space||Fly / Fall|
|Esc||Pause / Game menu|
|Tab||Release mouse cursor|
|Mouse||Direction of Movement|
In order to work with fullscreen, a window manager called Matchbox is used, but it has a side effect of the mouse not quite working right in the menu so you need to use a keyboard to start up a world. Once you are in the world, the mouse works just fine.
To exit, you can either click the x in the upper right of the screen or you can reboot your pi.