Great idea and very nice aesthetics!
I really like the idea of adding a preprogrammed movement loop to the base-defence game, but in the current version, it feels a bit too straightforward - often the best loop is just to put them in one spot near the base, or move between two such spots by the shortest loop.
So I was thinking of what can make it more fun - and I was thinking adding some rhythm to it would make it more meaningful, so you can adjust the loop to respond to the rhythm.
Or maybe even monsters spot not just in one location and go towards base, but they spawn in predefined spots, and move in a certain direction with some rhythm. So the challenge would be to make a loop that best fits those two.
Also, having separate tracks for archers and sworsmen would be fun!
Overall - great ideas and interpretation of the theme!