Quite amusing. I think finishing game(gaining all achievement) weren't too much of grinding, even though little. I would have liked some silly story attached top of the game. Or at least something like: "You finished game, congrats!" or "If you didn't notice, game ended... sucker".
Some random point:
+ I didn't notice any introduction, I might have skipped it, but this didn't need any.
- I would have liked to be able to skip buying of third ship, which I tried, but couldn't do.
- Achievements didn't explore other possibilities of game(like get in one run 1000 coins without killing any, or kill 10 enemy in one run without getting any coins)
+ getting new ships were just in sweet spot, amount of new stuff increased slowly but steadily (of course skills increased at same time)
+?- Achievements didn't have in-game purpose(unlocking). Or if they did, I didn't notice it.
In total, nice game but without context just running trough 'maze' is not rewarding. World in peril or maybe lunch in peril would have been enough. Game took just the time this kind of game should.
Verdict: Playable, amusing, non-rewarding