André wrote: Have you completed all levels of Enemy 1?

Almost. I'm trying to complete level 31 but it's very hard.

Authors say that "Enemy 2" has (about 30 new levels).
What is exactly the number of levels?

Oh, you mean THAT trick. Yes, I know it.
I thought there was a hidden/secret passage or something.

Thanks for your tips.
What do you mean by the "shortest path trick"?

My next problem is the shooting part (spaceship destroying) in level 21. The goal is to "find" 4 generators of alien spaceship and destroy them. The intro text says that I have to shoot the alien spaceship's hull with my cannon, and look for generators (they should be visible through the holes). I'm...

It helped a lot!
Thank you.

More info: I'm playing "Enemy TOV Easy Play", English version, installed with WHDLoad.
The room I'm stuck in is number 14.

I'm stuck in level 18. There is one room with a wall-gun and group of aliens. I always die there. How to pass?
Picture:
https://imageshack.com/i/ex6b0453j