I've read the others reviews, found them quite good and I thought I could write mine.
Even if this game is broken as hell, it deserves some mentions.

Basically, its a zombies 2D shooter with top-down view, controls on keyboard and aiming with the mouse.
3 main classes : - Heavy (resistance and damage) - Medic (heal and support) - Assault (speed and damage)
Each classes shares common skills for the 3 of them, and got its own set of class skills.
As you progress, u get 1 skill / level. max level is 100 and max skill level is 25.
That said, you can see how specific a build can become. And yes, you CAN fail a build (respec isn't free)

Gears are on 3 parts.
Weapons : 1 pistol and 2 main guns
Armors : 5 pieces
support : grenades and turrets
Weapons and armors comes in variations of base category (white, red, black), type of weapon/armor (lot of them = replayability) and augments slots.
Black gears are the best and only drops from very rare black chest, wich can be only opened with black key, wich can be purchased from the store, but also, can be dropped. see below.

Single player and multiplayer up to 4. The more, the better loot and xp. And difficulty.
Levels layouts stays the same, but the pattern, zombies and bosses are randoms, wich makes for replayability.
Faillure is not friendly. You lose all the loot chests dropped, still get the money and part of xp.

The main strenght of this game is its fast paced action. You got to aim well, shoot fast, see the type of enemy coming, move around to dodge and reload ...
The gameplay is amazing, and depends on your build, other players and way of playing.

I pretty much covered why this game is good. Or at least, have (had?) the potential to be cereal good ...

So the cons:
- Surprisingly, that game require you to have a high-end setup PC. I checked on chrome, memory allocation was like 1.2 gig ram.
Each time you start a level, you build the client, and If you don't have enough CPU/RAM speed you'll be slow as f**k which will piss you off, and piss the other players off too in the lobby, which make them quit .. and we have a nice rage loop. (Certified by CaptainALTF4)

- The lag IS real. It looks like a 80's garbage slomo. funny at first, but then ...

- The loot system. Another review here said the same : Totally random generated confirmed. I read about some level range .. like -40 / 10 (not confirmed).
So we got the grind and the casino. Guess what ? exhausting, frustrating, raging wil happen. And sometimes luck can happen.

- The elite drop, black gears and nightmare mode. I'll try this simple.
At lvl 35 you gain access to nightmare mode, the hardest difficulty. In this mode, you CAN encounter 2 types of bosses which CAN drop a specific type of chest wich CAN give you a black key (15% chance). And first, you have to win the map, wich is impossible (feels like you need some black gears already). And you only have 5 tickets/day.
No guys, its not broken balance, its made so ppl go to store, buy 200$ black keys to maybe .. maybe have some decent black with 9***/10***. Cuz still casino, ur black can be uber faillure. huehue.
Derp.
(And the 200$ isn't random, I really saw someone claiming to have paid that much for those keys.)

I dont mind paying some money for good games, even if its just cosmetic and minor bonus, if i do it, its mainly to support the game devs (and I will give a lil something for this one).
But for this game, the deal isn't fair.
It's crap load of real money for unfinished and buggy game to MAYBE get some more balance if you are LUCKY with casino looting shit.

And I found KongHack. Just some tweaks here and there, and now my gameplay is "even". Yes, I didn't want to rampage hack everything (so obvious to get ban), I just wanted to fix what I felt like broken.

Thanks guys, thats awesome.