plip.plop on 30 March 2015
Save file sizes seems legit, but that doesn't explain mobile versions, and the 360/PS3 versions, yes they are smaller maps but the game still exist on older hardware.
For the record, I do not play Minecraft, have never played or downloaded it. No interest in the game at all. But a game that has that much universal appeal, should make an attempt to be on as many things as possible.
