OK its a bad game. The so bad it is good type bad game.
Another of these Unity Asset Flips 1 level Part Naked Chick [Free DLC], Part Zombie Killer, Part FPS, Part Survival. A mixed cheap bag best bought for fast achievements and trading cards at sale cheap. However I found it a bit more stupid fun than those 1 minute instant jigsaw games.

So. At game start inside a backyard you pick up all 7 weapon double pistols, knife, bow arrow, rocket launcher, sniper, assault rifle machine gun. Hand around and keep collecting them as they endlessly re-spawn for stock ammo. Use mosue scroll or number keys to use. Except pistol all have right click default zoom. 3 rounds ammo collected is enough for all killing achievements to use all weapons. 5 rounds stocking enough. Exit by door. Outside go extreme left of broken road or better still enter right side behind a fence closed yard with an open door. See screenshot Attached:
https://steamproxy.net/sharedfiles/filedetails/?id=2900375358

Wait for waves. Stupid zombies get stuck at door and you can kill easy for 10,20,30.....100 kills 10 achievements. For achievements waves of 10, 20, 30, 40 come. Then they keep coming in loop for leaderboards. Save Rocket launcher when they are 20 ish. I killed 25-30 at a go using launcher and unlocked 30-40-50 kills at a go. Use rest. Bow and arrow + sniper were fun.

Game is bit clunky and running around the 2 blocks in small map may be issue. If zombies close in and attack lets say no defense works. Survival is meaningless since you can easily hide in some places or jump up the broken wall cement block in front of this yard etc. If you load up lot of endless ammo at start you are set. You do not need to play single session for leaderboards maybe. At least for achievements you do not need. You can finish achievements in 20 minutes and then see if you want to just keep shooting playing rounds for fun or leaderboards. Weapons switched may freeze in lag at times just scroll weapons with mouse move around zooming in out should solve it. Can be bad if you move around on road instead of hiding and get that weapons freeze some moments. Free DLC makes chick shooting naked. Developers have not bothered to polish up textures as that is not the target anyway. Still better than many of those dumped unity flip half finished games because beyond what I wrote there is nothing more to expect. Buy cheap at sale.

https://steamproxy.net/sharedfiles/filedetails/?id=2900375358

At end of 100 kills [if it does not register kill 10 more next wave] Gallery in Menu unlocks with 5 images. The menu pages are useless overall. Help section hardly has info, and Gallery you see 4 photos. Click each. navigating to 5th photo is useless. Use a Mouse scroll to reach it. That should do the game 100%. There is in game currency that keeps increasing with everything you do every round. with what use, no idea? Buying ammo? Could not find any inner store.

https://steamproxy.net/sharedfiles/filedetails/?id=2900375634

DO NOTE: If someone in family played the game in own account or if you play default on someone else's saves in local files the 10 Killing achievements will be stuck bugged. The inbuilt game currency will carry over to you and create mess. In that case play on different device or on a different guest slot for users in same PC/Laptop. In case more than one in family use same device to play.