sliders that go off screen is easy, just make a really big slider, or move part of the body off the screen in the editor, however this is unrankable. Really fast sliders are made with green lines that change what's called slider velocity, and a bigger number will mean a longer, faster slider, SV changes are rankable, within reason. there are also other unrankable things you can do with sliders, but you should probably learn how to make a good map before worrying about those.