IT is Ok. In fact I like it.
There are an upgrade shop (if you press spacebar). Well I suggest you to make 2nd part of the game and include as follows:
1. Different kids of enemies
2. Epic music. This one is not really suitable for such a game.
3. Include some bosses.
4. Include separate upgrade shop: additional guns, missles, support ship, the actual ship upgrades and etc.
Well I enjoyed the game.
u0435 %u0432%u0441%u0435%u043C %u043F%u0440%u0438%u0432%u0435%u0442!