Apps similar to Stencyl include Godot Engine, which is free and open source. Other options are Unity, GDevelop, Wick Editor and LÖVE. There's no shortage of Game Development Tools like Stencyl, with more than 100 alternatives for Windows, Linux, Mac, the web and Android.
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.
Phaser is a fun, free and fast 2D game framework for making HTML5 games for desktop and mobile web browsers, supporting Canvas and WebGL rendering.
United Kingdom
Adventure Game Studio (AGS) - is the IDE and the engine meant for creating and running videogames of adventure (aka "quest") genre. It has potential, although limited, support for other genres as well.
United Kingdom
Flax Engine is claimed the most agile game engine. It's open source, cross-platform and it lets you write scripts in C++ and C# seamlessly. Also focused on lightweight development. A true game changer.
Poland
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GameSalad Creator is an authoring tool developed by GameSalad, Inc. (formerly Gendai Games) aimed primarily at non-programmers for composing games in a drag-and-drop fashion, utilizing visual editors and a behavior-based logic system.
United States
Cocos Creator is a complete package of game development tools and workflow, including a game engine (based on Cocos2d-x), resource management, scene editing, game preview, debug and publish one project to multiple platforms.
Phaser Editor is a tool for HTML5 games creation. It provides several built-in editors for texture packing, JavaScript coding, Assets management, and 2D level building.
Xogot brings the full power of the Godot game engine to iPad. With a native iPad experience designed for touch, you can create, test, and share games wherever inspiration strikes.
[Multimedia Fusion 2 has been replaced by Clickteam Fusion 2.5.]
Game and software creation has never been easier or quicker than with Clickteam Fusion 2.5!
With Fusion 2.5’s amazing event editor system you are able to quickly generate games or apps.
Within your first hour you.
United States
FlashDevelop is a free and open source (MIT license) code editor for Actionscript (2 and 3), Flex (MXML) and HaXe.
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Bring your game ideas and concepts to life with 001 Game Creator, which gives you the power to create a variety of game genres. With simple point-and-click scripting, and high customisability of characters, monsters, items and magic, you can make anything possible.
Canada
DragonRuby Game Toolkit is a professional grade 2D game engine. It's tiny (~3.5MB), fast, and cross-platform (including consoles and mobile).
