Just ideas...
-Add improvements to speed and machineguns as well as to lazer. A shield (limited energy, use only when immobile) would be well too.
-Add more-than-a-hit-to-die mechs. Some may require lazer and machinegun, and/or in certain order.
-Add the diagonals!!
-And maybe a little animation between scene and scene would be useful for showing some other kind of artwork and anims; maybe even a "level choose" ("should we take the mothership through the Gray Mecha Swarm or the Red Mecha Surprise Zone (change names accordingly)?
-Firing enemy mechas. If they fire lazer, have them "charge" it visibly before firing (to allow to RUN AWAYY!!).
-A "chase the crazy hyperspeed mecha" level?
-An "ally mecha" (shoot that golden shining thing now! hey, you got an ally!) that moves with you and fires its machinegun with you. Maybe more than one.