If Indigo isn't quite working out for you - we quite understand! Here are some possible alternatives to help you get your game dev fix. Each of these suggestions has something in common with Indigo, there are of course lots of other engines out there!
Code-only! - If you're looking for a code only engine, try Haxe with Heaps. Battle hardened on commercially successful titles and increasingly incorporates functional programming ideas and syntax. Without going into the history, Haxe is a spin off from Flash (a notorious game dev platform itself, even today), but don't be put off by that; Haxe is very modern and does not require the infamous Flash Player to run.
Scala! - The only alternative Scala game engine at the time of writing is SGL (Scala Game Library).
Real FP! - If you're a determined and brave functional programmer that insists on all the typeclasses, it's Yampa.
Best in class opensource! - If you're looking for a more traditional game dev experience with an editor, aren't fussy about your language and want something opensource, you probably can't do better than Godot.
Happy game building!