I had so much fun with your game! Nice simple pixel graphics and for a week a very nice code base to keep going. You get an extra award for usability by adding the volume slider in the options - amazing! Most of the games are just too loud and when you play together via stream you always need to adjust the volume.
I hope you don't get this wrong but i had the most fun just breaking the game - as soon as i understood i could stack the towers on top of each other the enemies have been doomed haha. I played fast forwarded and killed the goblins so efficiently that i somehow jump from round 3 to 15 in under a minute :D VICTORY!