Games on Arcade are supposed to be 'simpler' but they won't limit you to just 2D puzzlers or anything. Think quick one trick pony type games that can be easily consumed and fit within the 50 MB limit. I went to IGC this year and met a few members of the Live Arcade team (had them play Aerial Antics too). I also mentioned the title which I debuted there "Oust" ... which I was told would be exactly what they were looking for. I'm essentially aiming all of my efforts for that platform because the type of games I like to make are better suited for that audience.