I entered ludum dare once or twice a few years back. Haven't got the time for quite a while (or i just forgot about it :b). I'm back this time with greater experience under my belt!

I used to use unity3d. I see lots of unity and ue4 participants. For this ld, I'm going for a different approach. React will be my tool of choice :). Along with npm, I'm confident that the efficiency is not less than other game engines.

Good luck, have fun!