flixel
flixel is a free Actionscript (Flash) library
Flixel is a free, open-source game development library written in ActionScript 3 originally for Flash, created by Adam “Atomic” Saltsman. It provides a lightweight yet powerful base framework to build 2D games: handling rendering, input, collisions, tilemaps, particles, cameras, etc. It was designed to be easy to learn and extend, useful both for simple arcade style games and more elaborate ones.