How do I [enemy spawn problem]

Hey guys. I am making a top down shooter and I am trying to implement a enemy spawn system where once you have killed all the enemies on screen, double the amount spawn in their place at random points of the layout. could someone please help me.

Thank you for your time.

Here are 2 ways to do it

1. Event objEnemy > is NOT "on-screen" | system > create objEnemy

Here you check if the object is on-screen and invert it. Then you run a loop for how many new enemies you want to spawn (the loop number could come from a variable)

2. with a variable

For every enemy you destroy you subtract 1 from your variable. If 0 then create new enemies and add 1 to your varEnemy

Working perfectly thanks for the help