Super cool little game! The artwork is really charming, you really nailed the cute pixel art style!The gameplay is also interesting, going on the roof to change wagons works well. I think the game needs some polish on how it's played and what i shown. i had some trouble understanding without reading the descrition (a prompt above the signs to build, and an indication of the health of the turrets could have helped a little bit.)
I also feel a little bit "defenseless"during the defense phase (quite a pun x) because I though I could fight back using my wrench. Also a little offset of enemies sprite could help to "read" how many enemies are stack on each others)
Cool little game, you did a great job!