Gave this a go today. Really well made, high level of polish! The graphics are simple but everything works together; the particle effects give it a nice bit of flash. I really like the detailed save and retry feature, and the medals are motivating to play for even though I'm not good at this type of game. The difficulty curve of the levels feels well-modulated and I like that damage taken is proportional to speed rather than the player simply having a fixed number of hits. 

Something that might be nice is if a player retries a level they just beat and dies, they could have a secondary option to advance to the next level instead of requiring them to clear the level again. I also feel the absence of sound effects; just a few well-chosen ones for thrust, taking hits, and exploding would really give the game a little more kick.

Overall you did a really good job with this.