This is a TAS (tool assisted speedrun). Basically you can play the game frame by frame, with save states to create a run that could theoretically be done by a human. There are no cheats used here just the use of frame advance and save states. More about TASes: tasvideos.org/WelcomeToTASVideos. The tool that I used is called Hourglass. It only works in Windows XP so I used a VMWare to emulate Windows XP on a virtual machine. I would not recommend anyone use Hourglass as it is really buggy and can crash or desync super easily. In case you are wondering why there are so many enemies and why they are so fast you can read more about it under "reallyjoel's dad difficulty" section: www.remar.se/daniel/ijiguide_secrets.php,