Very engaging game, I felt quite satisfied beating it.
A few points where it can be improved:
1) lower the sound volume, it's way too loud
2) make horse upgrade stack (it looks like placing more than 1 horse does nothing)
3) rotate the UI part for the animals to make it look like a rhombus - I was constantly forgetting what button to press to place what animal
4) remove some drawn UI elements like range for the turrets and especially that yellow line from the horse to the player. I get it that one needs to know those ranges, but those clean 1px curves just do not fit the game visually.