I agree with @Rasco, changing countdown to timer could be nice.
P.S. I don't have android phone, so i have to play in unity editor :)
Try to make WebGL build: it is pretty simple to do in Unity...
Viewing post in Sliding Puzzle jam comments
Wow you actually took all the hassle of downloading the code and playing it in editor (my dirty code got exposed :-P)
Yes the idea of making a web build came after the jam has begun and when I did so some UI elements lost their alignment and I didn't have much time to fix it. Will make note of it for future.