It was ok but it needs some key factors to be a good game.
Firstly, iy would be nice to be able to change the background, on offence but the current one is un-likeable.
After that a changable ship design, different disigns and maybe if you are advanced different atributes (speed, power and health?)
And the area, its a bit small so it would be hard to manuver your ship without crashing, so a large stage or smaller ship might be nice.
The wrap around was nice but unperdictable, like if you are sstanding at the edge you never know when a stone will wrap around and hit you in the back. If you keep the wrap around, and I suggest you do. Than try and make it so your bullets wrap around too.
The Shop and money: Well its a bit hard to collect the money so why not make the money bundles contain a little more money, and if not have the shop prices drop a little bit.
Levels: Well there are only 4 and it might be nice to have a few more. And if you want your game to be a contest of who can get to the highest level than why not tring to randomize the stones and the levels keep increasing.
Well thats all I can think of sorry if it took a lot of work and this comment is beating you down but it just needs a little more work.
PM me if you send out a new version,
P.S. I suggest you change the author comments section so that it's a little nicer and not so down.