Imagine Unreal Tournament not as an FPS but as a 2D side scroller. Get armed with a variety of weapons and go head to head by yourself or with your AI team members and try to rack up frags to win the round before your opponents do.
Even though there are some obvious bugs, they can be overlooked for the most part. I would also choose medium of even low quality in the in game options because it can run "laggy" at some points. Still, it is an impressive set of actionscripting that went into this Flash game.