I realise that one reason for Minecraft's success is that it can run on older/weaker computers, but this is crazy.
What you're seeing here is Mojang's world-builder running on the Raspberry Pi, a tiny hobbyist computer that's little more than a glorified chipboard, and which costs only $US35.
The version of the game has been modified to accommodate the Pi's limitations (and is free!), but come on. The fact you're looking at any kind of Minecraft running on a computer that costs less than most retail games is bananas.