Thanks for checking out my game! I was really happy with some of the art I made, but with the backgrounds being so plain I wasn't sure what someone else would think of it. I'm glad to hear it looks good.
I tried to keep the tutorial quick and minimalist, but I guess I relied too much on players being familiar with tower defense games already. I'm not quite sure which detail was poorly communicated, so here is a (hopefully) more clear explanation of the game:
The goal is to prevent enemies from reaching your castle. You can do this by placing towers on the Loop. There is no limit on how many towers you have, instead you spend points to place them, and you get more points by defeating enemies. Also, towers can be placed on any tile of the loop, not just the corners. Once you defeat all enemies the next level is unlocked for you to play.