Where to start? HL, HL2 or other?

[atomicjello]

A few years ago I discovered botmans excellent site and had great fun playing around with some basic bot programming in HL.

I'm back at it again, but I'm not sure how to proceed. I'd like to start with HL2, but I can't get a feel if that is a good idea or not considering the limitations in the current SDK.

If starting with HL2, is there a link to a framework? Maybe Valves' SDK has something - I thought that was the case but haven't found anything.

Maybe HL2 isn't even the primo bot engine anymore...

I guess I'm looking for recommendations (engine, bot frameworks, etc), given the current state of things.