Just started playing this for the first time - excellent game! However, for such a well-received game, I'm surprised at just how little information is available about the game itself.

My question is this: do the natural resources (crystals, metal, etc) respawn at some point after you pick them up, or is there only a finite amount available? In other words, am I guaranteed to always be able to make more ammo, or do I need to be stingy with how I use it?

Also, do enemies that I kill ever come back, or is there just a set number of enemies on each stage?

I'm not certain, but I think that the natural resources do indeed respawn, but that most enemy soldiers do not. I think that soldier patrols might respawn, but the ones that are guarded set locations, like camps, will not respawn once you clear them.

Anyone know for sure?

After playing through Shamazaar, I've probably seen enough to answer my own question:

The following DO respawn
Crystals
Metal
Vegetation

The following do NOT respawn
Troops
Ammo
Other "non-natural" items