I found some weird glitches when leaving and starting the game again a couple of times, where towers began looking like white squares in shop and sometimes in the game.
I think shop could have a graphical button or some hint towards controls in the gameplay, to avoid the need to go look it up in the main menu, because most other stuff are pretty intuitive.
And also I think the sounds could be tweaked to fit the main melody, like Super Mario Maker did with block placement, but that would probably be hard to do in a jam.
Apart from that, I had fun!