Hmmm...
I'm a professional Half-Life player for having played the 3 single-players (Half-Life, Opposing Forces and Blue Shift) more than 300 hours...
The start was good, but TOO SLOW! You have remade some things well, but the graphics still weren't really good. If I was you, I wouldn't do an Half-Life remake, but a Flash Movie telling its story. This is the best Single Player game (according to me) so dont try to remake it of any way, because that will only make your things got blammed.
The Sounds were okay, because you taken them from the Original Game. You should have remade the older textures in paint or Photoshop instead of trying to make some strange 3D with them. Also, the walking scenes were boring and useless. Instead of doing this, you should have made your game longer.
According to this, you made an ok thing, and if you continue your works, please pay attention at what I just said so you can get more skillful at Flash Gaming.