SC2Mapster

How would I go about making, say, a fireball that follows a straight path when fired, does damage over time to any unit within a certain radius, and explodes after a few seconds?

Search for tutorials on collision-detecting missiles, specifically piercing ones.

Short version: Launch Missile->Behavior on missile unit->periodically applies Search Area/Damage effect (short period length, behavior duration equal to intended missile lifetime)->Search to apply damage or just use splash damage->final effect on Behavior (on expiring): Suicide to kill missile (or use missile lifetime on the Mover of the missile)

You might need a "kills to caster" effect if kill credit is relevant. Iirc there's also a way to use a Persistent effect on the missile which still credits the original caster instead of the Behavior on the missile unit. I think it's the Launch Effect field in the Launch Missile effect.

So I tried duplicating a missile weapon and all its assets, reduced the speed in the mover, and added a buff behavior to the missile which applies a create persistent that does 4 damage every .1 seconds for 100 cycles. However, the missile appears to self destruct immediately after being fired. What am I doing wrong?

You don't need a Persistent effect and a Behavior. Behaviors can emulate a persistent effect on the unit.

I assume you didn't exclude player units and/or missiles from the damage effect, and since missiles have low HP by default...

@Photoloss: Go

Thanks, I just increased the health of the missile, and it worked!

You really should exclude missiles (and invulnerable, stasis, dead) from damage effects. You don't want this fireball to be able to kill flying yamato missiles or the like, do you?

@Photoloss: Go

I excluded missiles and self, etc. from the damage search effect, but I couldn't figure out how to exclude itself from the actual damage hits. But for all intents and purposes, it's fully functional.