Ranked in these QuestionsQuestion Ranking
Pro Powerful language
Pro 75+ demos
Pro Fully free
HaxeFlixel is fully free and open source.
Pro Uses Haxe
(excerpt from source): To help you do this, the (Haxe) toolkit contains three main components:
the Haxe Language - a modern high-level, strictly typed programming language
the Haxe Standard Library - a complete cross-platform standard library
the Haxe Compiler - an incredibly fast cross-compiler
Pro Getting started guide
Pro Active development community
(excerpt from source):
There is a multitude of channels to interact with the community:
Our google groups forums
#haxeflixel on IRC (freenode.net)
@HaxeFlixel on Twitter
The HaxeFlixel organization on GitHub
The HaxeFlixel page on IndieDB
Join our development chat on Slack
HaxeFlixel group on Steam
Pro Modelled after Flixel
But with considerable improvements -- the HaxeFlixel team are constantly working improving and fixing the HaxeFlixel API, as compared to the original Flixel which is no longer updated.
Pro Outstanding community
The HaxeFlixel team and contributors are very active on Github and other community places (like Slack), and are usually able to respond to your questions within a day or two.
Pro Hardware accelerated rendering on native platforms
Pro Similar syntax to Actionscript 3
Haxe's syntax is similar to AS3, so Flash developers can transition to HaxeFlixel if they are familiar with AS3/Flixel.
Pro Powerful debugger overlay
You can watch variables, log (trace) messages, and check for memory/frame rate performance.
Pro Easy 2D game development
(Haxe)Flixel does a lot of things for you like tilemaps and collision detection, which makes it super easy to create 2D games.
Pro Cross-platform IDE environment
On Windows, the IDE of choice is FlashDevelop, but if you're looking for cross-platform IDE (Windows/Mac/Linux), there's Sublime Text which includes a package for Haxe syntax highlighting, as well as auto-completion.
Pro Cross Platform
The open source Flash API is powered by OpenFL, which allows you to compile to Windows, Mac, Linux, iOS, Android, and even major consoles (coming soon).
Con Small community
HaxeFlixel devs are not as large as (example) Unity devs, so the amount of support and exposure is limited.