It's pretty good, although I found out you can just attack them head on, as if it wasn't a stealth game.
Enemies reacting to your steps could help out a lot there.
Maybe it'd be a good idea to also make a indicator above their heads, telling you when you're being spotted, but as it is the string is fine.
Attacks also seemed to pass through enemies without them reacting, if you're standing too close to them.
I don't know how you're handeling the attacks, if it's a box collision or a line trace, but if it's a line trace, maybe try and make it a sphere trace instead?
And if it's a box/sphere collision box, then try and make it bigger.
I think that about sums it up. Keep up the good work!