HaxeFlixel
The Flash framework Flixel moved to the Haxe language, so its 2D games could outlive Flash and ship to web, desktop and mobile from one codebase.
Adam Saltsman wrote Flixel in ActionScript 3 in 2009 and built Canabalt with it the same year — the game that more or less invented the endless runner. Flixel became one of the go-to frameworks for pixel-art games in Flash: sprites, tilemaps, cameras, simple collision and particles, with refreshingly little to learn.
As Flash headed for the exit, the community ported it to Haxe on top of OpenFL, around 2013. Haxe compiles to C++, JavaScript and more, so the same game could ship as HTML5 and natively. Its best-known product is the rhythm game Friday Night Funkin' (2020), whose open source code made the framework a lot of teenagers' first taste of game programming.