TD system (spawning enemies)

[STH]

How do I make a TD that goes like an ordinar one - when the first round of monsters are gone, the second one starts in 20 secs or so. I am pretty sure this has to be something with conditions, but I am not very familiar with conditions. could som1 help me with that?

 

[mase]

Use the

wait until being the number of units ownd by (the creeps player)

Oh and u can look at this TD tut

 

[lesson]

as i've said before that toturial still needs something.. there are nothing saying what to do with:
Gold Income
Coundtdown Timer
and other triggers as well...

and also with the creep spawn... in the toturial it says "each 45 seconds of game time" .. in the most td's the creeps spawn, lets say 30 seconds after the creep wave before them has a coundtdown timer to see when the next lvl begins.. in the toturial it will make the creeps spawn nomatter if the first level are still running... the creeps will simply spawn each 45 senconds of game time.. it wont say like "Level Completed" or anything or wait until the lvl before them is completed..

though many of the other things in the toturial are very cool, and kinda nice to know.. but still it needs some more