It's heavy challenger, but need more work, like a score, a start screen, sounds, colors, new elements like lifes, cheats, stages (starting of a easy one), special moves who consomes time...
Interesting, but repetitive. Some uppgrades like other monsters (flying monsters maybe?) and another towns (again, with flyings buildings), more than one type of draw lines (other colors, new functions) may turn this game a good one.