Even better, Haxe.

The language is very familiar for AS3 devs and it transpiles to performant C++.

Many games such as Papers Please have been made with Haxe.

There are numerous engines/libs for game devs:

http://kha.tech/

https://www.openfl.org

https://github.com/haxenme/NME

Just to add a little more... Haxe not only transpiles to C++, but it also transpiles to JavaScript. With a Haxe codebase, can deploy a project as both a native app and on the web. Really nice for games especially.

Haxe is really amazing. Currently my favorite ones are Kha and Luxe, though the new version of Luxe has been on development for a long time;

Kha is really nice and I like using it. It's amazing that the author developed a specialised IDE (granted it's a modified version of vscode) for the framework.

The quality is so very high, much much higher than a typical open source project, because it's not just a bit of code, but an entire toolchain and workflow. So much so that an entire engine is built off this framework! https://armory3d.org/

I am currently using Haxeflixel game engine for a trivial project and I am enjoying the overall experience. Haxe is a great little language a8the engine is fully featured. The basics like scene management, gui, pathfinding etc are bundled in.

I also tried Heaps which on paper looks amazing but could not proceed due to lack of documentation.

Dead Cells is another recent high-profile Haxe success story.

Nooooo. Flash is dead, thank god.[1]

1. https://www.rystedtcreative.com/tech-talks/flash-dead/

I remember steam games were made in Flash a few years ago. Doesn’t it just export to HTML5 these days? Isn’t it used / couldn’t it be used to make a steam game?

Yes, it does. Adobe changed its name to "Animate" once they got the HTML5 export working. Dunno if it's in use for any games nowadays.

You can also AOT compile, so that would be another option.