Making An Enemy Wave System?

Alright, so I've done a bit of looking around, and I've already found a few different threads on this subject. However, none of them have given a good explanation of how they exactly did it.

I have a layout, with spawners spread on all sides. What I want is a way to manage different waves, so that each wave will add more enemies, and allow me to spawn different types of enemies depending on what wave it is.

Can anyone help me with this? I can provide a .capx with a base to work with if anyone would like to do it. I'm not asking for someone to do it for me, but I just need to understand it, as I'm having trouble figuring it out.

Base capx download.

Lucky Boy ... I made you a 1 event spawner

Just Change the NumOfSpawnedEnemy for the base spawned zombies and the rate of progress for the number of added zombies each round !

Link

Hmm, I don't think it's complex enough for what I want to do. I think I'm scratching the wave system and going more with an infinite progression. (Think Super Crate Box, if you've seen it.)

I'm trying to get it so that every X number of seconds (within 3-6 seconds, randomly), pick a random spawner, which will spawn one of 3 different types of enemies (again, randomly.)

I think I can figure it out, but I need to figure out how to do:

Every X Seconds (between 3-6 seconds).

Instead of just:

Every X Seconds.

Then, I need to figure out how to make it spawn a random enemy from a selection of three different enemies, from the randomly picked spawner.

Sorry if I'm asking for too much, but if you know how to do what I'm talking about, maybe you could explain it to me?

<font size="5">EDIT:</font>

Wow, I feel really stupid for not checking the manual first. I found the random seconds thing: (Random(3,6)), still looking for making it spawn a random enemy type on the picked spawner.

<font size="5">EDIT 2:</font>

Sorry, I figured it all out. I think I needed to write out what I wanted to do to actually help me think about the process. Thanks anyway!

That happens to me all the time, I can't work something out, then I put up a post and 5 minutes later I've solved it. It's as if writing it out makes it clearer in your own head :)

Very nice example, — Thank you.

Yeah, thanks for the help Whiteclaws, sorry about that haha.