Longford
A cross platform Lua based game engine
... and scaling of sprites.
+ Box2D physics engine.
+ Play sound effects using WAV files and stream music using OGG files.
+ Automatic tweening system
+ Texture atlases so that many Bitmaps can be "cut out" of a single larger picture file.
+ Supports user-written shaders for advanced graphic effects.
+ Automatic resolution scaling.
+ Supports OpenGL or DirectX backend