In the first GMTK in 2017 I committed to it and sure enough was able to finish a playable version/game/prototype.
Last year I didn’t have the time. This year, no hard commit either and so not enough time to finish a fresh project like that in just two days.
I don’t think the prototype I have this year is far enough that it is interesting or clear what it is. It’d probably be better to just describe the game design that was planned. :)