Vaccine

Every time you bring the vaccine back to your friend you go up a rank and get an achievement. The house will shift and randomize, you'll earn extra time and you have to go find the vaccine again. (If you solve the mystery of the house the game will end and you'll have to start a new game so ignore the light beam puzzles and notes when going for the rank achievements.) To get all the rank achievements you'll need to be fast so just get the vaccine and bring it back to your friend but try to collect as much as you can so you can survive. The first time going through is the hardest since you only have the knife to start out with. You'll need to find a pistol and/or shotgun and some ammo so you can kill the tyrant by the vaccine and get the custom pistol. After that it will be downhill (as long as you have ammo) you just have to hope you can find the vaccine fast enough with each rank and don't run out of time. There's a lot of luck involved since the house is sometimes bigger and harder to find the vaccine or you might run into a lot of crawlers without having a gun or repellants or you might not find much supplies/ammo or a firearm.

You also get XP and can level up your stats. You want to level of your aiming since it will make your guns do more damage and also your health since you'll take less damage. Also leveling up your luck helps you find more supplies.

I made a video giving tips on how to play/survive and also how to solve the mystery of the house:


good luck