Ruthlessly difficult - especially for dunces like me who use a trackpad - but with a very appealing aesthetic and a nice variety of obstacles, though I haven't gotten far enough to see how exactly progression is executed (simply surviving is challenge enough). I particularly like the notion of using projectiles and 'enemies' as a means of defending oneself, having them neutralising each other and allowing for a perhaps surprising aspect of quick-time strategy. The means of unlocking new spaceships relative to the time you can stay alive is well-done and easy to understand as well. The few I've got are also visually sufficiently distingished and tend to have charming flavour text along with them.
For a game that isn't really of my favourite genre it is excellently made and i cannot give it less than five stars for what it is.
..just maybe a difficulty setting would be nice for people who like a slower pace - giving them a chance to look at the nice designs and such? A purely selfish suggestion, I admit ^^