Thanks, I must admit that sleep deprivation and obsession played a pretty key role in the development of this game.
I had a ton of fun but I definitely need to take a break for a bit :)
The theme connection isn't obvious, but it mostly has to do with the digging mechanic.
As you are removing tiles, and then swapping the world, those tiles you just removed now become solid blocks.
So the LESS tiles you have in the current world the MORE you will have in the swapped world.
Maybe a stretch :)