OK some crit;
The enemies can kill you in 1 hit, yet you have to blast them 5 or 10 times to kill them. Enemies appear far to often considering the amount of shots they take to die.
When you jump, you "float" way too much. The gravity needs to be increased for the fall rate.
Clearing the first set of spikes without getting blown out of the sky by the flying ships is pretty much impossible. I tried about 20 times and didn't get past them even once.
Graphics are really nice, and the game reminds me of Master Blaster (which is one of my favourite oldschool games). I also dig the mouse and keyboard control, even though trying to play it on a laptop with no mouse attached is kinda super difficult since i have to cross my hands over to reach the arrow keys (there is no chance in hell of using the mouse trackpad thing with my left hand).
I would recommend having W,A,S,D as alternate controls to the arrow keys so people can use what they prefer.
Overall a great start, but yeah... add a health bar, make the enemies die a tad easier or decrease the spawn rate of them (especially for level 1), and make the vehicle fall faster after jumping.
Thanks everybody for the comments. As far as difficulty is concerned, I like difficult games so I don't wanna make a stupid - easy game. I 've added a mini map so that the player can see if an enemy approaches before he makes his next move. Remember it's not only a shooter game but also has elements of strategy and adventure. You must first destroy some of the floating ships and then try to clear the spikes. I also increased the gravity. You are right, floating was a little bit annoying. Tonight I' ll add an option to use W,A,S,D for movement as many people prefer this setup.