ZDoom

Hello ZDoomers, i am rather new to modding in (Ultimate Doom Builder + GZDoom). I've seen how some terry wads and others have unique attack patterns, like projectiles launching from a spiral, how would i go on about making some of these unique attack patterns? (Example in image.)
Thanks, and i hope you guys can point me in the right direction so i can make more interesting fights in my wads.

Spam the same call to A_FireProjectile but change the angle parameter, and the zofs parameter, I believe.

If you have a WAD that does this, try looking at its code and see if you can tell what's going on.