Pretty good, but needs tweaking.
The game has two issues that keep it from being any challenge whatsoever. First, you can survive really easily by just holding the up or down keys until you reach the level boundaries and then switching directions. Second, the obstacles always spawn where your guy's Y location is, which makes the first part possible and also makes it so that when you get the gun all you need to do is stay still and hold the spacebar to kill every obstacle in your path, since they all spawn directly across from you. I recommend adding some random spawning, as well as obstacles that can change their path, to keep this interesting. I also recommend there being checkpoints of some sort so that when you become really powerful later in the game, you don't have to fly through the same easy boring obstacles at the beginning and skip to more challenging sections (but that give bigger rewards). I also recomment pointing out the store when you first start the game. I didn't even notice that box in the corner until you mentioned your game had a store in your response to another's review.
Other than those minor issues (which can be fixed without too much trouble), this game was really well done. Happy Clock Day!