High performance UI layout library in C
Godot Minimal Theme
A modern, cross-platform Quake game engine based on FitzQuake.
Game engine supporting many 3D/2D formats and graphic effects
C++ lightweight cross-platform game engine
The multiplayer game engine
A game engine for console based text games
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
DOOM / Heretic / Hexen source port with enhanced graphics and UI
A cross platform Lua based game engine
scriptable game engine with built-in support for 2D graphics and sound
Built to be ease of use, with no programming knowledge, Multi-platform
Free Android 2D OpenGL Game Engine
A very small multi-platform game engine for creating desktop games.
Open source, moddable game engine for the "Polygon Love 2" game
Little game background framework in java.
Gomoku Game: Playing with Computer