Width

Most the games I make are 1280 x 720 because I like that window size and I don't think it's too unreasonable to assume people can view at that window size.

But I can't upload my games to the arcade because of the 800px width limit and, well the games are made now in 1280, can't really change them.

It's been on Tom's todo list to add support for fullscreen games, we just have a lot to do. FYI according to our site stats about 10% of people don't have screens wide enough to fit 1280 wide still, and consider it might be far too big for mobile too.

Yeah I understand you guys have a busy schedule! I'm in no rush :) I'm not focused on mobile games but I find that full-screen feels more immersive than a window.