Co-op zombie shooters come down to two things. Whether the guns land with any punch, and whether you and your mate can really cover each other. Left 4 Dead is the right reference and a merciless one to invite in. What a browser version has going for it is is friction, or the lack of it. No install, no lobby faff. Bring somebody or don't bother.
The premise is precisely what it says and not a step further. Shoot zombies. Bring a mate. Fine as a starting point, but there's no hook here that Left 4 Dead didn't already supply, and co-op horror needs pacing and pressure rather then bodies simply walking towards you. Feels early. Not one I'd point people at yet.
There's no more worn out setting than zombies, so tone is the only thing left that matters. This one wears its Left 4 Dead lineage out in the open instead of smuggling it in, and thats a fine target to aim at. It isn't constructing a world so much as borrowing one you already know by heart. For a short co-op run, that will do.
