Retro Space

When the powerup appears (I only saw it once!), there ought to be an audio cue- a more eye-catching, animated sprite for it wouldn't hurt either. I second the critiques in the other comments. This game had something that saved it from the abyss of a 1/5 rating; it is probable that with a few tweaks this would be a solid 3 or 4.

??? I finally made it all the way to the end and beat the green boss, and... nothing. Not even a "you win" message, no constant looping of levels. Really, it shouldn't be that hard to add a simple end test and message (even if it is only temporary), nor would it be to constantly loop the levels, adding a little extra life to the enemies.

Would be good to have a visual or accustic confirmation, when you hit the enemy

Good, but a few issues: 1. enemies start shooting before they're visible -- this is particularly annoying with the boss. 2. If two enemy shots hit you at once, two lives are taken (which is okay, I suppose, if that's really what you want; usually, there's a short "get ready" invulnerable period... Which should also occur at the beginning (no mouse-to-keyboard races, please. Ideally, game would be frozen until keyboard input is received)). 3. If there is no reason NOT to fire (no ammo, no overheating, no accuracy bonus, no enemies that chuck shots back at you), why not autofire? 4. The very sparse powerups only seem to have one level. Instead of the generic "P", maybe you could have "V" (for V shot), "II" (for double front shot), and "^" (for a slow but powerful wave cannon, or maybe a shot that follows the player's movement)...? These wouldn't be cumulative, necessarily, but player could try to get them or not based on whether they want to use that weapon.

this has potential. toss us some powerups, and perhaps lengthen the chiptune loop you're using for BGM so it doesn't seem as repetitive, and this could be quite good.