Game: Survival! (Version - Highly based off Half-Life engine similar to GMOD Map: DN3DE1L4

once you start in a crashed submarine, get out of it by pressing correct combinations (spoiler: they are 1 & 3) then get out and find a scuba gear! once you got it, avoid the octabrains! swim to the surface and kill any troopers and turrets that appear! get the blue key and get to the factory. let yourself be picked up by crane but be warned there is a mine so if you touch it and have less than 80 health, you will die! after you get picked off, kill the policeman, grab the shotgun and the red key. go down to the alley but be careful as there will be 5 policemen after you, kill them all and use the key! you will be shrunk down to tiny size and have 10 seconds to return to normal size but PLEASE choose correct way! left is wrong, right is the way! also there is a fucking troopers that will wait you in the other room until you grow back to normal size. if you manage to survive, kill them and activate the switch, shrink again and return to main room. if not, enjoy your little squishy death! go underwater and fight with every monster (including octopus brains) and get to the surface. once done correctly, activate the door and will open underwater! be careful as there are more octopus and a crusher! dodge carefully and you will arrive at waterfalls. here you kill more monsters and then go at the puzzle and time your pistol shots! if not done correctly, you will fall and have to go again. once done, run through acid and don't forget to pickup the boots as they will protect against acid! once you avoid the flying octopuses, exit the level! however before that, there is a crack in wall but you need explosives so blow up the crack and you've discovered the SECRET LEVEL!

thus ends my walkthrough of THIS LEVEL!