Unless there is a way to see or check the whole prompt that made this game, it is hard for me personally to say if this is impressive or not as I don't know what percentage of this was vibe coded. I also see there is an incentive to skew the truth here, as there is a substantial prize pool and that usually makes people become very creative.
In the past, I was trying to reproduce vibe coding results when I managed to get all the information from Youtube videos (model version, ide version, same input data and prompt) and never was I able to reproduce something impressive even after multiple runs of the same thing.