I really like the blocky style. A song would go a long way on the difficulty ramping though (I saw on your credits that you had music, but I had just the shooting sounds when I played).
The tutorial was a bit confusing regarding the "shop auto refresh", I assumed the shop was the lower part of the screen. Alsom, "Everything cost 2G" could be on the same line, to be clearer.
The firerate and the range blocks are a bit complicated for some color blind people to differ, just a heads up.
I really wish I could rotate blocks.
There could be a very rare "1 tile" block, that could be an easy mode haha.
I didn't understand exactly what counts as a tower, each tile is considered a tower? So a 4-sized block creates 4 towers?
Overall really cool tetris/tower defense mash. I managed to last 4 minutes only.