The tutorial shows all the controls and gives you an oportunity to test them out. The game drops the play straight into "a world gone mad" where people start attacking Hank immediately. Hank arrives without a weapon and must fight and kill until he can get one. As more enemies arrive he needs to pick up other weapons pretty soon.
Madness Interactive has been viewed over 13.2 million times as of May 2012, making it one of Newgrounds's most viewed submissions and by far the most popular Madness-related submission on the site. The game won the Daily Feature and Weekly Third Awards when it came out, and has a score of 4.2/5 and average review of 9.4/10.