When creating challenge levels in Rktcr, you have a variety of options for platforms beyond polygons. In the second part of my tutorial series on level editing Rktcr I cover three other options: arcgons, subdivision-smoothed polygons, and level set painting.
Each lends itself to a different sort of level design and layout. In the rest of this news post I will briefly describe each; for more detail check out the full tutorial.
Arc-gons

Arc-gons are polygons with circular arcs at each corner. These are good for precision control of ramps and jumps.
Smoothed Polygons
Smoothed polygons are the result of applying a subdivide-and-smooth algorithm to a selected polygon, resulting a more organic "gooey" style of curved platform. The nature of the subdivision gives you less precise control than of arc-gons, but the resulting forms are more organic.
Painted Levelsets
While the other primitives I've discussed are connected to a control polygon, Rktcr also allows one to specify level geometry as a contour of a painted image. This allows for crazy, natural, almost "wet" forms, with lots of fragments and splatters (if desired).