Here to take a look at creating your own platform games?
The most convenient and easiest way to create your own platformer levels is to get a level editor created for an existing game. Below are listed some popular level editors. A lot of editors based off existing games are still in development. Try searching for a level editor for your favorite game!
Super Mario World – http://fusoya.eludevisibility.org/lm/index.html
Super Mario 64 – http://homepage.mac.com/qubedstudios/ToadsTool64.htm
Most of these level editors take some familiarization to get used to – but for the most part it’s either all documented or easy enough that you can just pick it up. If you have any questions, feel free to visit the forums!
Programming your own platform game from scratch can be a lot of work, and it almost isn’t sensible to cover everything on this site. However, here are some good resources for developing your own games for the GameBoy Advance.
There’s a wealth of information on GBA development, GameCube development, or development for PC systems on the internet if you look. But again, the work is not something to shrug off. If you wish to undertake this type of development, a good amount of patience will go a long way. Good luck!