Not a side-scroller, but here's a screenshot from a terrain generator that I wrote: http://i.imgur.com/HgMWbXe.png http://i.imgur.com/HgMWbXe.png the white do

Not a side-scroller, but here's a screenshot from a terrain generator that I wrote: http://i.imgur.com/HgMWbXe.png http://i.imgur.com/HgMWbXe.png the white dot in the center is a control point that the user can drag around. That point defines a mountain. Height decays exponentially with distance from the control point. The height function is perturbed by an underlying noise function. Edit: It's all done in JS/WebGL using a fragment shader and blatting the output onto static canvas elements. These are then composited for the larger image. It supports scrolling and zooming. I could never get the performance quite to where I wanted it.