Clunky, cluttered, and craptacular.
In all honesty, it was hard giving this game even one star. First off, the base gameplay mechanics are, as the title says, clunky--at best. In many cases, I found myself lagging, despite my respectable system, which was made even more unbearable by the "camera" system, which almost instantly switches directions the moment you move the cursor behind Freeman.
The music isn't even music. It's a 3 second loop of the same 5-note drum beat, without any noticeable change. The sound effects are sparse. In fact, I rarely even heard anything EXCEPT the music.
As for the physics you touted? Well, let's just say that Isaac Newton is rolling in his grave right now.
The parody was hard to stomach. Yes, I understand it's a parody. What I don't understand is why the common perception of parody is purposefully poor writing and stale jokes. I skipped as many dialogue instances as possible.
The graphics are also quite terrible. The blood is red yarn, characters are quickly slapped together and stiff (and yes, you could have hidden the joints a lot better than you did), and the backgrounds are either bland, gradient-filled blocks with physics objects slapped in front of them or the same thing with low-quality replications of in-game objects from Half-Life 2 slapped on top.
Finally, the most atrocious part of this entire ham of a game--the constant misspelling. "Conrols." "Shot your enemies." I admit, I am a bit of a grammar and spelling Nazi, but this is ridiculous regardless.
I think its safe to say that despite whatever time you spent on it, it is one of the worst Half-Life themed Flash games on this site. I'm normally not this cruel, but come on. This is ridiculous.