ImpactJS is a robust, well tested, and experienced HTML5 game engine. It continues to be maintained frequently and has a large supporting community that encourages the further development and refinement of the framework.
The ImpactJS framework has extensive documentation making getting started an easily guided experience. It is designed to work on all devices including mobile including iOS.
Ranked in these QuestionsQuestion Ranking
Pro Excellent collision detection system
Many plugins are available, including one called Impact++ which adds features like pathfinding and dynamic lighting.
Pro Level editor
Built-in map editor with support for tiling, collision layers, and actors.
Pro Extensive documentation available to support development
Pro Truly cross-platform allowing developers to build for anything
Extending the reach of a game developed with ImpactJS is easy due to the cross-platform nature the framework. There are Considerations around performance, resolution and audio, however all can be appropriately addressed when in development. Works in the browser via Canvas, even on mobile. Easily translatable into a packaged app.
Con Cost of $99
While most HTML5 frameworks are offered as free open source projects, ImpactJS has a one time cost and no free option.