Start off by using the mouse to draw your level. Use the "G" key to toggle the grid. When your done drawing your level, press the spacebar to render the level. Use the mouse to place the player, then use the arrow keys to play. Note: Because the clone limit is 300, especially large levels may not be able to render correctly.
I thought it would be cool to make a platformer level creator. I wanted it to be quick and simple to make any design you wanted, so why not just allow users to quickly draw out their levels? :-D Everything here is my work, except for the player movement script, which was made by @MoreGamesNow Thank you, @Z-dimensions for some help. :-)