Really fun concept - in execution I think the map felt a little slow paced, and since you cant perform many actions other than timing when you spawn creatures it can take a little while to build up so it doesnt quite fit that 'strategy high'. I think with some polish, and maybe the ability to choose spawn zones/switch paths your creatures walk down, an extra layer of strategy could be added!
The art style is great though, I love the tower and creature designs!