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Godot is a fully featured, open source, MIT licensed game engine. It focuses on having great tools, and a visual oriented workflow that can export to PC, Mobile and Web platforms. It is a cross-platform 2D and 3D game engine and game development IDE.

Unreal Engine is a professional suite of tools and technologies used for building high-quality games across a range of platforms. Unreal Engine’s rendering architecture enables developers to achieve stunning visuals and also scale elegantly to lower-end systems.

Scirra Construct is a 2D game development engine with a focus on building games visually. No programming is required though the software uses a visual method for event handling that relies on programming concepts like variables, loops and conditions. It provides a powerful form of scripting that's as easy as clicking, dragging and dropping.

Continuing the legacy of Mark Overmars' Animo and Game Maker, GameMaker: Studio is a proprietary game-creation system which can export to multiple platforms including Windows, HTML5, Linux, iOS, Mac and Android.Often considered the fastest and easiest-to-use cross-platform game IDE technology, GameMaker: Studio allows developers to create games in a single codebase and then publish them to run natively across a wide number of mobile, desktop, and web platforms.

An open-source 3D/2D game engine for ObjectPascal.

Adventure Game Studio provides the tools to make your own adventure, for free! Bring your story and artwork and slot it in, and let AGS do the rest.

Pygame is a set of Python modules designed for writing games. Pygame adds functionality on top of the excellent SDL library.

The Atomic Game Engine features a cross-platform editor with deployment to Windows, OSX, Linux, WebGL, Android, and iOS. Applications can be built using JavaScript, TypeScript, native C++, and C# scripting is in development. The Atomic Game Engine is a full source solution under the permissive MIT License on GitHub

One framework for creating powerful cross-platform games. The spiritual successor to XNA with 1000's of titles shipped across desktop, mobile, and console platforms. MonoGame is a fully managed .NET open source game framework without any black boxes. Create, develop and distribute your games your way.

Open RPG Maker is a free and open source clone of features from the RPG Maker series (i.e. rpgmaker200, rpgmaker2003, rpgmakerxp), as well as many other features. All of the data files are in XML format and are easily editable with any text editor.

Cocos2d-x is an open-source and cross platform open source free 2D game engine for mobile game development known for its speed, stability, and easy of use

The WorldForge project is the original open-source MMORPG project, dating back to 1997. The intent lies in creating a widely used development framework and set of libraries by motivating interested developers to improve on the original code.

A cross-platform 2D game prototyping framework based on OpenGL and C++.