Slender Fortress is composed of several maps, all different with a variety of bosses hunting the RED team down as they search for pages. However, the goal can differ, such as instead waiting for Escapes to arrive. All RED members, regardless of class, are heavily modified to fit Slender Fortress's gameplay. They all walk slowly, but can sprint under the limit of a stamina meter, are reduced only to their melee weapons, and wield a flashlight. The flashlight can run out if used for too long, but it charges up when shut off. An interesting note is that while the BLU team can see and hear the RED team's chat, it is not vice versa since the BLU's chat is automatically silenced by the (TEAM) command so the BLUs can't distract or annoy the REDs.
Once a RED player is killed by the boss(es), they will be immediately sent to the BLU team where they can travel around their own map, armed with only a melee weapon, and can kill their own teammates and gain all of their weaponry once they enter the PVP arena. The BLU team can also spectate the RED team through the eyes of a ghost with the by typing in !slghost and enabling the command.
For the RED team Edit
- Melee: As aforementioned, the RED team are only allowed to use their third weapon, which is in all cases a melee weapon. While all bosses are unkillable (excluding a few who can be stunned), the melee mechanic can be used by picking up pages. This can be done by placing your cross-hairs over the page before pressing Mouse 1 (the default attack key) and hitting it. Note that using a melee weapon can and will alert the boss if they hear it.
- Flashlight: The flashlight is a ray of light that emits from the RED members once they press Mouse 2 (by default). It is used to light the RED team's way, as most maps are very dark, can be turned back off with Mouse 2, and will automatically turn off and stay off for a few seconds once it runs out of batteries. However, when off, the batteries will recharge. Some bosses can be stunned by a flashlight, such as the Rake and Kate.
- Blink: The blink mechanic, inspired by a similar mechanic from SCP - Containment Breach, is a mechanic that forces the player to blink every few seconds. They can also blink manually with, by default, the R key. While the blink mechanic seems useless, it is used for certain eye-based bosses like the Weeping Angels or SCP-173, who move extremely quickly when no one is looking at them, but cannot move once being observed.
- Sprinting: As aforementioned, all RED members are reduced to a slow-walk by default. However, they can sprint, greatly improving their speed, with Mouse 3 (the scroll, by default, is encouraged by most servers for the sprint mechanic to be binded to the Shift key). Sprinting for too long will slow the REDs down, as signaled by them breathing heavily and the stamina meter running out, so preserving your sprint only when necessary is an important factor.
For the BLU team Edit
- !slghost: If the BLU team want to spectate the RED team while they're being hunted down, they can type this command into the chat and enable it by pressing 1. They will then become a ghost who can follow the RED team. However, they cannot interact with the REDs, and the REDs cannot see them.
- Proxies: If a boss like Billy or Giant Zombie Soldier are present in the playing area. Some of the players from BLU team will be selected and a notification on the left of your screen will pop up (this applying only to the selected players) with reminders and hints at becoming a proxy, if you select yes you will spawn in a random location of the current playing area. Proxies can come in different forms. Proxies that can take the form of a Soldier, Pyro, Demoman, Engineer, Sniper and or Spy. Depending on which proxy Master is the boss they will get a skin resembling a monster or creature from the same game, movie, story as the Proxy Master. To signify a proxy has entered the playing area a groaning sound will play, there will be a control metre, the control will slowly deplete until it is empty when emptied the proxy will die, you can kill people from RED team to gain control. Proxies can also be killed if battling a RED team member and losing. Proxies can also all gang up and kill alone or small groups of players which can be a useful advantage.
All classes have the same walking speed (but not sprinting speed) and have their normal health. The Frying Pan and Golden Frying Pan have been blocked.
- Scout: Scout, when sprinting, is the fastest class and has a 15 increase for the sprint meter, and swings his melee weapon much faster than the others. However, he is the weakest class, as most non-one-hit-kill bosses can kill him in very few hits. The Sandman, Boston Basher, Wrap Assassin and Atomizer has been blocked.
- Soldier: Soldier wields the second most amount of health, able to withstand many hits from non-one-hit-kill bosses, but also possesses the second slowest sprint speed. As of February 2016, The Disciplinary Action is only blocked when a proxy boss spawns. The Equalizer and Escape Plan has been blocked.
- Pyro: Pyro has regular speed and regular strength, and the only major pro is being resistant to fire and afterburn. As of February 2016 the Powerjack is only blocked when a proxy boss spawns. The backscratcher has been blocked.
- Demoman: Demoman has identical strength to the Pyro and also has a 66% increase for the sprint scare meter. Most of his weapons have a longer reach this can be useful for stunning bosses or getting pages at a further range. The Chargin Targe, Splendid Screen and Tide Turner does not work and doesn't reduce fire and explosive damage. The Scottman's Skullcutter has been blocked due to stunlocking with long range, and The Ullapool Caber has been blocked.
- Heavy: Heavy wields the most amount of health of all classes, but also possesses the slowest sprint speed. The gloves of running urgently if applied give the heavy 80% sprint increase. As of January 2016 the Eviction Notice and Holiday Punch are now blocked.
- Engineer: Engineer possesses low health and average sprint speed but has 33% increase in battery life and can have his health increased by the Gunslinger by 25 HP. This class is also useful against flashlight stun bosses on maps without infinite flashlight. The Eurekka Effect has been blocked.
- Medic: Medic is a very useful class as his health regenerates when wounded by a non-one-hit-kill boss. The Medic can also see his teammates' location once they call for Medic, but the bosses mainly go after the Medic even when faced with a large group. The Amputator has been blocked.
- Sniper: Sniper wields low health but has his blink rate decreased by 40%, making him the ideal class against eye-based bosses like SCP-173. His health can be increased by 25 HP if Darwin's Danger Shield is equipped and he can heal 4 HP in a second if hurt if Cozy Camper is equipped.
- Spy: Spy's low health is identical to the Scout's and the Sniper's, however is almost always the ideal class in most situations since every sound he makes is 35% quieter from a boss's perspective. The spy cycle when equipped and on fire you can completely extinguish yourself. The Spy-Cicle, Conniver's Kunai, and Big Earner gets blocked when a Proxy boss spawns.