Hi,
I have a similar feeling as Calum, I am kind of disappointed with my game. I can try to justify its lack of content by telling myself I didn't have time to get more done thanks to coursework and exams, but of course opportunities like this competition don't arise often.
The main thing I found hard was dealing with Unity. This is probably my fault (since there are many great game designers that use it well) but I really dislike the design of the engine, and so a lot of time was spent wrestling with getting Unity to work how I wanted, rather than making the game.
I also agree that when we got given the base game it was tricky to come up with an idea, in the end I just played safe with a style of game I'd already made in the past (so that I knew what I was doing). I wish I could've come up with something more unique and had the time to implement it, though.
I wish everyone good luck with the judging, and I'm sure whoever makes it through will have deserved it!
Peter