Can I add gravity to my game?
From OHRRPGCE-Wiki
Yes and no.
It is possible, using very advanced plotscripting, to use the OHRRPGCE to make a side-scrolling game with gravity. Examples include complete games such as Siv: Journey of an Egg, Trailblazers, or tech-demos such as Baby Bob the Hamster or Moogle1's Super Mario Bros demo.
However, this is not a built-in feature of the OHRRPGCE, and is not reccomended for anyone who does not have an advanced knowledge of plotscripting — and even if you do have and advanced knowledge of plotscripting, it is easier to program a side-scrolling game from scratch in another programming language than it is to do it with plotscripting.