I initially had no idea what I was supposed to do, but once I figured out the whole dragging thing it was alot of fun! I enjoyed the open puzzle structure and the ability to draw whatever path I wanted. Unfortunately, I got stuck on level 7. Even after killing everything (and drawing paths of repeating circles to ensure both units would target all enemies, because sometimes they wouldn't target those flying bug things), the portal still wouldn't let me move on. I have no idea what else I could do in the level. Outside of that, very nice.