Can it be your computer/laptop that you can's score more points? Did you read the manual written by the-gorilla? I did but I noticed that the laser doesn't always works and if the misile is too far to the left I can't get it back. My highest score was Level 26 and about 1000 points but I never did beat myself since I try the laser.

Btw start shooting even if the ailiens aren't visible yet and lean back.