Two Nights at SMBX.org is a kind of horror fan-made game based on FNaF series. The game has several parts that can be downloaded for free, including part 1, part 2, and two episodes in part 3. You should check out all of them to experience further challenges. Once joining, you must undergo two creepy nights and have to face lots of wicked animatronics. Just show off your surviving skills, use your tactics and always keep an eye on the surroundings. Wish you luck!