Gravity Hook is a flash game created by Adam Atomic (Canabalt and Flixel) and Danny Baranowsky way back in August 2008, and marks their first collaboration. It was based on a typing-tutor prototype game called Gravity Key, created by Arne Niklas Jansson. Arne gave his permission for Adam to develop a mouse-based version that scrolled onward and upward forever. The original Gravity Hook was created in 5 days on a very early version of what is now the flixel framework.