Yeah I agree, it really needs more interesting enemies or even challenges. In fact I originally planned a more complex gameplay, but ended up not having time for it... Partly because I spent way too much time making pixels of the GB LCD Screen have shadows and all ^^. Not a very smart move, but I had so much fun that I don't regret it !
I also spent one full day on the song which, again, should have been done after the gameplay was finished...
The fill algorithm is quite simple, when an enemy dies, I search for the closest tile that can accept gore. Meaning a tile that has less gore than the current one but that has neighboring tiles at least at the same level of gore. That way I end up having a pile that "spreads".
Visually it is just a tileset with 4 levels of gore per tile and 3 backgrounds to chose from (all ofthis in 4 variants).
This is the complete Level TileSet, It's quite limited due to the gore system limitations, but I didn't really mind as in the end the level just gets obscured by gore.
This mechanic of body piles is actually quite fun, I'd love to find a good idea gameplay-wise to make good use of it.