I enjoy this game (not this exact one, the actual game that inspired this one) and so I was happy to see someone made a flash version, and I enjoy the use of Pinhead and Micheal, but this looses points on many levels.
The glaring obvious is that this plays more like a game mode rather than a whole game. Meaning, two-player (especially local only with no online multiplayer option) is a possible selection in a game mode menu, not a standalone. Next, there are no instructions. Like many people, I grew up playing this game, but I have on rare occasions met 1 or 2 people that had never played it before. If someone like that were to find this game, they would have no idea what they are doing. They might eventually figure it out, but games should always have some instruction with them. As much as I enjoy the game this is based off of, it still needs some level of added flavor. Having the thumb nails of Pin and Mike are a nice touch, but that is all it is, a nice touch. Then there is the fact that there is no sound, what so ever.
Having brought up so many flaws, I feel that I should offer a little insight for possible ways to improve (beyond correcting what has already been pointed out). Adding some sort of story line would help this submission, in my opinion. Even if you just did some sort of dramatic comic book-style opening sequence of the two talking smack like they are about to throw down and then they play this instead to settle their differences. Next, add a computer opponent option. I know that falls into the category of "already pointed out" but, seriously... computer opponent. I know it is not something that would directly affect game play, but making the bars two different colors will help make the game more visually appealing as well. It is interesting to see who played what bar, but beyond that, the two colors will make the game look less dull. That or add some sort of background using dark colors and make the grid a brighter color (or colorful background with dark/black grid).
Other than that, the game is well programmed. I have played versions of this in which even once a player has the majority of the squares the game goes until the entire grid is filled, which I find to be a waste of time (in chess you stop once there is a checkmate, you don't play out the inevitable), so I enjoy that your version stops once a player has the majority of the squares.
Over all, the game is well programmed, but seems to lack planning. I highly advise updating the game and resubmitting.