Size Antimatters I liked it. Though i wasn't really sure if I should dodge or run into the falling hexagons. Some of them were differente, so at the beginning I thought they were power ups or something, but I didn't feel any great difference, maybe some sound effects and a flash on the screen when colliding to indicate if it's good or bad to collide?
Other than that, I don't really think it's common to 2~4 people play the same game on one PC at the same time, specially a flash game. Maybe a simple race with a highscore charts would do. But that is just my opinion.
I know how hard it is to make games in so little time, I love participating game jams too, and from what I'm used to see as results I can tell you did very well. Your resulting game is really great, congratulations. :D
