Hm, firstly, Rei IS an experienced user, but that isnt on topic, so, secondly, a 2d sidecrolling game uses no 3d elements but panels or other 2d elements - that's why it's called 2D. Thirdly, most 2d sidescrolling games I know aren't jump'n'runs like your gravity sample is, but auto-scrolling space shooters or something comparable. Am not too sure if this is the basic definition of a 2d sidescroller, so please correct me if Im wrong.