Oh java. How I despise your puzzle. But that's not your fault. I've never understood how to solve these puzzles! It was on theme with the fact that time is counting down, and you did very well to get this done when you didn't think you'd have time to take part in the game jam.
Constructive (*honest) feedback: The empty tile should be a different colour to the background of the image I believe, so it's more clear where the empty is to the player. The music was nice, and I liked the idea of the pitch increasing as the time decreased - however it did start to hurt my head - but that's probably because I getting frustrated at the puzzle I couldn't solve!! <3