I like the concept, and it ran fine for me in Chrome. But here are my critiques after playing the first three levels:
The controls are annoying at times. QE camera rotation is too slow to really want to use, I'd need that on MMB drag or something. Placing stuff is finnicky, and it's very easy to accidentally make barricades that let zombies slip by. It's kind of annoying and unnecessary that the things are placed at a fixed distance from the player. Rotation here could be improved too. If you do place a barricade unnecessarily, you permanently waste finite resources (until some upgrade).
You should really not be using Esc and F1 as binds in browser builds!
One time they ended up smashing my barricade. I guess I blocked the path entirely by accident? I didn't think I did.
I am not sure what the warning about gathering the objective summoning the horde is about. It makes a loud noise, but otherwise it doesn't seem to do anything special. I ended up over-preparing for it.
It seems oddly stressful that locations are not repeatable, so it feels like you may risk falling behind if not farming enough exp before leaving locations. And then add permadeath to that. Although exp didn't really seem that important, so maybe it's fine.