Nice game
I loved it, but I found a glitch that took me to the 25(would have gone farther, but i got bored, and the ufo was stuck to the right of the screen and another one wouldnt come out, so no power-ups :(). All you have to do is wait until you get a game over, pause, then unpause, and you'll be back in the game, but you're ship will be invisible. (note: doesnt work if the aliens get to the bottom of the screen)