I think this game could be made more challenging if the shadings (pink boxes) varied in the later levels and if the fields themselves were rotating (making it harder to orient oneself). Other than that, 4/5 for interesting concept.
It's an O.K. game. I like the splats, wish there was more blood. I've experienced the same sort of "invisible line" type of deal when trying to move my mouse to collect the coins (much like that described by evilbob). Kind of glitchy, kind of good. Gets a 3/5 from me.
 "25 Boxes"){kind=icon}
 "Pillage the Village"){kind=icon}