Tempest

What I did to obtain this is just stay in one line and just keep shooting and I waited for all the flippers to come into my path when they are on the outer rim of the shape. I am not sure what level I got it on because achievements are unlocked when the game is over and you have lost you life. I just stayed on the outer rim of levels 1 to 5 and waited for the enemies to come to the outer region. However you have to time your shooting correctly or you will get terminated. Not sure if its supposed to happen but after you shoot a certain amount of enemies you gun starts to shoot faster which should help.