A certain block game
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Open source simulation game based on Transport Tycoon Deluxe
Free game engine for development of desktop, mobile, and web games
Desktop/Android/HTML5/iOS Java game development framework
Solar2D Game Engine main repository (ex Corona SDK)
Cocos simplifies game creation and distribution with Cocos Creator
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.
Soft-body physics simulator
A free transportation simulator game
FlightGear Flight Simulator: free open-source multiplatform flight sim
A strategy game with a high fantasy theme
RTS game with the theme of Strategy by Design
A planetarium software that shows a 3D simulation of the night sky
Seven Kingdoms: Ancient Adversaries
Chess Database and PGN viewer
3D Engine c++
For exploring cellular automata like Conway's Game of Life.