I think this game is way too hard, or I am way too bad. What certainly would need some work is the UI, for example, in the shop between waves I had no idea how many souls I had and what I could buy. I don't know if any new enemies are introduced later in the game, because I did not get there.
Another issue I see are the collisions and the navigation of the enemies. I feel like the enemies just go in a straight path to the altair, but they could use some simple pathfinding algorithm.
To also be positive, the audio design is great and the cutscene at the beginning is just top-notch.
The game could use a little work to unlok it's full potential, but overall it is a nice base-defense game.