Very nice game. Got score of 443 points.
I appreciate that restarting moves you back to beginning of level, and not all the way back to the start of the game. Although the "Try again" button does not explain that clearly :)
Assets and polish look great and the transition from underground to the sky in lvl 2 was amazing. And the big planet in last level... Great, immersive music too.
Although I usually don't care about scores in games, you made collecting coins and gems so satisfying that I tried to collect as many as possible - often resulting in death :D - great job there.
Cheers!