I've actually never played CS at all, either vanilla or Source. I have the HL2 silver package, and IIRC Condition Zero is basically a single player version of CS, right? Would playing through it be a good way to learn, or is the learning curve at this point too high to have any fun for a new player? I've tried CS:S once and quit when I'd get killed within the first 15 seconds and then twiddle my fingers for the next 10 minutes.