Thanks for the feedback! You described exactly what I had in mind when creating the game. Since this was my first game, my main goal was simply to see whether I could make something at all. Because of that, things like balance and game design ended up taking a back seat.
By the time I realized it, it was already too late to change much :(
So I balanced the game in a way that lets the player make it to the end and eventually overwhelm the tower with a massive zombie horde.
Anyway, I really hope you still enjoyed the game!