Revised strategy for the laziest of people (such as myself): Unlock fake walls, block off all entrances but one, funnel all zombies into one hallway, extend that hallway around yourself so that it's closed off from the rest of the map completely and the only way to get to you is through the zombie spawn area (btw, make sure collision and demons are off). Then, stand at the end of the hallway, face the zombie spawn area, pull out your pistol, hold down the fire button, and click away from your browser to fire indefinitely. Zombies will funnel into the hallway and be killed by your infinite ammo pistol. Inevitably, some zombies will use this game's really bad physics to glitch through the walls, so you'll have to check periodically and kill them. You can essentially win the achievement automatically using this strategy.
Turn on all of the things that the achievement says are allowed, block off one entrance of the first map with fake walls, block off the second one with a few layers (I did 3) of walls and a hallway in the middle for you to shoot through, take out the pistol, hold down space, then click away from the browser so the game auto-shoots with the infinite pistol ammo. You'll be able to go do something else until level 21, but because the zombies clip through the walls if they stack up enough you wont be able to leave forever. It shortens your painfully dull playing time for the achievement by a good margin, and if the game's physics weren't so poor the achievement would essentially be automatic after the initial setup.
I don't like the delay between hitting the restart button and the level actually restarting. It throws me off, because pressing a button while that delay is still in effect doesn't do whatever that button's supposed to do when the game finally restarts, so I'm stuck holding down the button waiting for my guy to do what he needs to do, and I die or miss what I needed to do and have to restart again, rinse and repeat.
Scratch my previous comment, you can mute but you have to be in the game, you can't mute from the menu. You lag when you get achievements, but you get way too many achievements. Also, upgrades take a second to reach their little slots, and you have to wait that out before you can use them. Additionally, the game pauses when you move your cursor to the menu area, but not when you move your cursor outside the screen if it isn't through the menu area. Still 2/5
Boring game, basically all of the levels are "roll/push this object into this other object to overcome this obstacle while also bouncing on enemies". Also, 3 kinds of enemies. Including the boss. Why have different enemies at all if it's going to be so limited? Not to mention the fact that we're supposed to feel good about orphaning 3 newborns. Seriously. 0/10 would not play again unless they added more badges.
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