Many games in ludum dare are made with an engine such as unity or unreal. This is fine and has many advantages, but it can be more of a challenge using a self made game engine and porting it to other platforms with your own skill. Bonus points if it is a 3D game. Extreme props to you if you use bare OpenGL/SDL(or similar framework).

* Leave your custom game engine games in the comments. Especially the 3D ones! :grin: *

I have done just this in my custom made 3D game: https://ldjam.com/events/ludum-dare/38/ids-journey