I don't know that most people will be playing the games on mobile devices. Newgrounds is a flash website, which means people play it on a real computer (or maybe old Android that had flash). I don't think that just because these games are HTML5, they will suddenly use the site in a different way.
Anyways, the design philosophy for my game is single-touch, so that it can be played with a mouse as well as a touch screen. Beyond that, any typical flash game ideologies should help - quick, responsive gameplay, pick-up-and-play, replayability, aesthetically pleasing.