Easy achievement. Start up a "normal" game. (Don't do this in the 5min game)
Now, the main point is to move around. So, don't kill all enemies. If there's only 1 enemy, let him be. (This will give you more time to fly) Pass him and move around behind him. Back and forth or from left to right. If there is more than 1 enemy, kill all of them, until 1 is remaining and repeat your moves behind him.
I was able to get this achievement before I met the first boss.