Terasology

godot

Godot Engine – Multi-platform 2D and 3D game engine

imgui

Dear ImGui: Bloat-free Graphical User interface for C++ with minimal dependencies

raylib

A simple and easy-to-use library to enjoy videogames programming

GDevelop

🎮 Open-source, cross-platform 2D/3D/multiplayer game engine designed for everyone.

Babylon.js

Babylon.js is a powerful, beautiful, simple, and open game and rendering engine packed into a friendly JavaScript framework.

libgdx

Desktop/Android/HTML5/iOS Java game development framework