Just a little explanation: I use a spells-as-powers magic system in
my wiki.
I built a chain lightning spell
here and a fireball-like spell based on the same idea
here.
Both are based on the idea of giving a spell multiple passes with the Homing Enhancement, with Cosmic allowing it to keep going regardless of hit or miss. The fact that it strikes at a new target each time is a special effect.
I hope that helps. It's a pretty straight-foreword method.
Edit: Oh, I forgot that the chain lightning spell uses the Over-Penetration rules instead of using the Cosmic enhancement. It just goes at new targets after over-penetrating (special effect).