Very fun! The main thing that I think could be improved is the visuals. Mainly the text's font, and the simplistic blocky tiles (Just some more detail). Some level numbers would be useful (ex. level 12/14), since I got pretty far (I think) but didn't know how many levels left there were. Another nice thing would be an infinite mode (If there isn't, like I said I didn't make it to the end) with the ability to spawn whatever blocks you want and place them on a grid however big you want. Also some kind of pause menu for setting would be good too.
This games main focus was definitely the gameplay though, and it did that VERY well!