So the mechanics of this game are quite simple: You get hit once (by bullet or ship), you lose.
For every shot that hits an enemy ship, you get 1 point.
In order to unlock all achievements, you need 200 points in one run. At first glance this seems a bit hard.

First off, the game has a very simple rotation of enemy ships. They will always appear in the same pattern and even their shots follow a pattern (which is pretty bad randomization).

Also, your ship can back off further down than is visible on the screen, so always do that in order to increase the gap.

If you stick to the left or right corners, you should never get hit at all. So the simple solution is just to AFK there until you're done.

However, there are also powerups in the game. They add additional bullets up to 5 max. So whenever you're able to grab one, leave the safe corner and go back immediately afterwards. This will make it much faster to reach 200 points.

You will die if you accidentally hit an offscreen bullet (by being partly offscreen yourself). So try to remember that a bullet that has just left the screen is still dangerous, or you'll have to move up until you can see your entire ship to make sure you're not killed by something you can't see.

Now you can hit infinite points and unlock all achievements.