• This achievement seems very hard to get, but this method is very simple since it's basically just spamming. I wouldn't call this super beginner friendly, since there are precise timings in the form of minor movements and knowing right when to start firing. Despite this, most players should be able to use this method even if they need a little time.
  
• Be sure that you do not form a dual fighter, since that will invalidate the achievement. If you'd like, you can also watch an unedited clip of me getting the achievement here:

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2554083604

1. Get to stage 7 by any means you'd like. You can get there traditionally, or you can select stage 7 from the start of the game. To do this, you can go to Settings > Game Settings > Select Round > ON, then choose stage 7 at the start of a new game.
   
2. Line yourself up with the center of your screen if you are not already centered
   
3. Start firing right as the Galagas start to converge to the center of the screen
   
4. Keep repeatedly firing until all of the Galagas are destroyed
   
5. Start firing again once the Boss Galagas and normal Galagas cross paths
   
6. Shoot down any remaining Galagas once they reach either the top center of the screen or the bottom center of the screen. Be sure to compensate where the Galagas are heading by moving either left or right.
   
7. Reposition yourself to the center of the screen
   
8. Repeat steps 5 and 6
   
9. Line up your fighter roughly in between where the "8" and "0" are in the high score on my demonstration
   
10. Start firing on the incoming Galagas
    
11. Continue to fire and make subtle movements to the left of the screen in tandem with the Galagas
    
12. Repeat steps 9, 10, and 11, but make the following changes
    
13. Line up your fighter roughly in between where the "1" and "5" are in the high score on my demonstration
    
14. Start firing on the incoming Galagas
    
15. Continue to fire and make subtle movements to the right of the screen in tandem with the Galagas

There you go. This was my method of completing the Single Perfect achievement, and I hope you found it useful or that it helped form your own strategy. Please leave any critiques, suggested edits, or anything related to this guide in the comments. Thanks for reading!