I like a challenge in my HL1 mods these days, but I have had to put this down because it is far too frustrating. There are a number of spots where the player is actively robbed of their health. This is level design 101 because you can never predict how much health the player has, unless you have taken steps to ensure that they are maxed out.
There have now been three occasions where I have had to enable godmode in order to progress because I'm constantly below 25HP and either taking unavoidable fall damage (vent drop into gonome corridor) or being jumped by multiple enemies with little to no cover (three vorts at the bottom of an elevator) and unfair fights (Just had three alien grunts spawn behind me and I only have 5HP). This means that I am playing through the maps by slowly peaking corners and glock sniping enemies, rather than engaging in fun combat arenas.
I don't know who playtested this, if anyone, but I don't think this has been tested on Hard. There aren't nearly enough medkits or healing stations beyond the opening few areas.
Other than that some areas are just a little silly. The generator room with the endless spawning zombies, I could see them appearing out of thin air and killing one immediately spawned another. I just kept running around until the door opened to save ammo.
With a bit more testing testing and and a few more passes to add detail to the maps, this could be an enjoyable little map pack. Currently, it's just a little unbalanced and bland looking.