Enable the "Debug mode" code. During game play, press the button configured as "B" on the Genesis. Sonic should become an object somewhere on the level. Press the button configured as "C". You can "paste" that object in the level. Press the button configured as "B" again to resume game play. Press the button configured as "A" on the Genesis while editing the level to change the object. You can also move the object in the air, etc. to truly make your own challenge. Also, you can move across obstacles and turn back to Sonic to cut points in the level.