This is a Platformer creator that allows you to make your own Platformer and play it afterwards. To select a block, click on it or use numbers 1-8. To set a block, click on the place where you want it to be. Once you're finished, set an end flag to mark the end of your level and click 'Export to save it'. (If the screen freezes after you imported a level, wait a few seconds).
Credit to @TimMcCool for the original project 'BLOCKY scrolling platformer creator v5.3'. Go check out his account and give him a follow for all the epic work that he does!