7, because...
The boss is buggy, laggy, and fucking annoying.
I came across two different bugs, one where I'd be teleported to the upper right hand corner, and one where I would randomly die, mostly when I was near the upper right hand corner.
Laggy, because of the flashing background. Enough said.
And annoying, because what you're meant to do isn't made clear. I got sick of trying to fight and checked the reviews. So I started to avoid, which isn't a great thing on its own, but as soon as the chicken started to move erratically, it would glitch and I'd go from full health to dead.
Otherwise, good game.