here's what i think:
-you should say in your tutorial that to buy new towers you need to spend points you get by killing ennemy.
The begginning feels endless and the game is really boring when there isnt a real challenge (like the boss or ennemys with a lot of hp) i think you could make the pacing of the game faster,
I think the most fun part of the game was to sell the tower to place it to another place so it does more damage to some ennemies with a lot of hp, too bad you don't sell the towers as much as you buy it.
I think you should remove the moments where you have to wait to get all the little ennemies kill, or making them less long
I didnt feel any difference in the gameplay depending on the type of ennemies (i didnt do all the levels though ).
Other than that, all you've done for your game is really impressive, good job!
I did a game too, feel free to test it and to give me feedbacks :https://kamigarp.itch.io/climb-the-tower