Having played around with hammer making a quick HL2DM map I have come across a small problem.
I have fallen in love with source mapping
Making your own materials with bump maps is actually a lot more enjoyable than slaving away at low res panel texures in PSP and wally.
The possibilitys are endless. (Don't knock it until you've tried it is the best way to put it really)
*Urban slaps self for doubting source.
This means that I know have 2 options. I can either make The Urban Project in HL1 while still messing with the Source engine and maybe make the sequel in the HL2 system or I can make the entire series in HL2.
Of course this game is entirely user decided on a multiple choice system so here are your options.
A)The Urban Project
or
B)SkyLine City : Source