Alien Outbreak 2: Invasion image - Haaf's Game Engine

Haaf's Game Engine(HGE for short) is a Open Source 2D Game Engine and is published under the The zlib/libpng license and is free to use even in commercial applications, however it makes use of the BASS audio library for sound, which is free for non-commercial use, but for commercial use you will need to purchase BASS or use a different audio library(BASS can be simply disabled).