Black Mesa: Re-visit the world that started the Half-Life continuum It is freeware. Enjoy the original again. Download speeds are amazing too. *Edit* After the 4.7GB of the Source Engine SDK, the full game is 11GB and some change. Bear that in mind if you run a SSD like I do where space is a premium.
If they added co-op it would make fans of the original cry foul. It would be like making the original Star Trek feature Vulcans that had unpointed ears. Most people would not care. But hardcore fans would go totally apeshit. The original Hlaf-Life was a classic. It was immersive in a way no other game of the time was. Playing Black Mesa now is almost painfully dull compared to modern games. But at the time of the original it was drastically game changing in a literal sense. It raised the bar higher than most games could manage to compete with. Again back to the Star Trek comparison: I hate watching the original Star Trek now. It is awful. But I recognize what it did. And I would also be offended if someone tried to "Edit" it in most any way. It is to sci-fi what many unmentioned religious texts are to their respective faiths. Black Mesa walked a fine line. They just put the original in the Source engine. Nothing more was really changed. It is a masterpiece.