A side project of mine has been dedicated to understanding the core concepts of 3D programming. Basically what I've been doing is refreshing myself on the C language and pulling apart quake source code. Keep in mind that this probably wont be involved in my next game but so far I am enjoying the challenge.
As far as Gulag goes, I'm debating on making a version for the Nvidia Shield TV and have been looking over some of the google services api to make that possible. There are some roadblocks involved in that project, so it really depends on how distracted I get with other things as well. I like my little game engine but it definitely needs some TLC if I want to develop another game from its source.