I want to make two sprites to gradually appear after that a group of sprites are destroyed.

To Tomycase:

How the horizon laser cannon works:

The horizontal cannon is moving from right to left and at the extremity of the laser cannon, there is a long vertical laser ray that moves from right to left at the same time that the horizontal cannon are moving. And like the code indicates the vertical laser ray disappears every 4 seconds and reappears every 8 seconds.

It's not because I didn't answered that I didn't see it, I'm not always available, get my own stuff to do too, anyway;

I'll be looking at your lazer code today, did you test what I sent yesterday for your turrets?

(also there is an edit button if you need to add something to your post instead of reposting one)

Did you make sure that the turrets lasers got destroyed at some point? Otherwise it will create more and more objects on your layout, give it the "Destroy outside layout" behavior, or destroy the lazer if not on-screen by events

My take on your cannons : i.ibb.co/jwdHjbJ/Example3.gif

The code:

I used a "On start of Layout" trigger but you can use whatever trigger you want (a function for example) to setup the cannon's laser; I gave a boolean variable to the laser sprite "Active" that I toggle on/off with a function (so it doesn't rely on a loop);

When "Laser" function triggers, if laser boolean is false, it will turn it true and change its visibility/collision enabled, and the opposite if true on "Laser" trigger; be sure that boolean is true before running the events, otherwise it won't work as intended;

Edit : I think your slowdown comes from a loop somewhere in your events, I'd need to look at your project capx if only you agree ofc, but that way I can check what is going wrong

Yes, I have tried the cannons methods and it works. But the game is slowing down and stops each time that I make a test. These are pictures of the two loops that my Event Sheet contains. I have tried to locate what the problem is with the "Debug Layout" button but I really don't understand how to detect a problem using that option. Here are the pictures of the loops:

To Tomycase:

Ok, I notice that there is a number located next to a sprite named "sprTurretsLaserRay" who is rising to 4, decreasing to 2, rising to 8 and then decreasing back to 2 again. Maybe this is the area where the problem is located. This is a picture of my Debug layout page. Maybe it's going to be helpful.