When you first launched Minetest, didn't you think it was just Minecraft? Actually not. Although their interface, style, and gameplay are almost the same, Minetest is essentially a free, open-source and cross-platform voxel game engine (written in C++ and Lua, using the Irrlicht Engine). It was created by Perttu Ahola and first released in 2010, and is now developed by a team of volunteers, with significant contributions from the community. It's available for Linux-based systems, FreeBSD, Windows, Mac, and Android platforms, and provides an API for users to create their own games and mods written in Lua.

Counter-Strike (full name: Half-Life: Counter-Strike) is a multi-player first person shooter game series officially released by Valve Software in 1999, whose founders are Minh Le (AKA: Gooseman) and Jess Cliffe. It was originally just a game module for Half-Life, and finally became an independent game after being acquired by the developer of Half-Life - Valve. Its game development engine is from the original GoldSrc engine to now Source engine.

Project I.G.I. (AKA: Sneaked, IGI is short for Institute for Geotactical Intelligence) is a series of tactical first-person shooter (FPS) PC game with realism elements and excellent graphics & sound effects design. In particular, the whole game comes with fantastic sandbox maps and playing methods, there are even dedicated servers built by fan players for online play. That's why it's so popular that it got numerous positive reviews from players around the world the time it came out (it has been 18 years as of this post, but AppNee is still willing to give it good praise).