Nearly all video game protagonists stand in awe, fear and wonder at the nigh-indestructible nature of the common wooden door. But what few of them realize is that their enemies also hold the same feelings of alien terror and incomprehension for them. In fact, most of them are even more afraid of these doors than the heroes are, because while it may be a pain in the neck for a hero to get one of them open, for the enemies such a feat is nigh impossible, even if said door has already been unlocked. Many of them lie awake at night in fear that they may have to face a hero who has actually figured that out, because such a hero will inevitably make use of Tactical Door Use.
When the player is able to close and open doors at will, he or she has complete control over where his or her enemies can and cannot go. When chased by a massive mob of foes, all you have to do to get out of it is hide out in a closet until they give up. Additionally, clever door configurations can make you turn an attack on all sides into a bottleneck assault you can easily deal with.
Needless to say, the games in which this trope appears tend to be Nintendo Hard
or at least approaching it, as it takes a truly outmatched and desperate individual to see doors for the brilliant tactical instruments that they are.
- Geneforge starts using this trope in the second game. The enemies you face are incapable of interacting with doors in any way, and what with doors being, well, doors, they're extremely plentiful, and on the higher difficulties they can be exceedingly useful.
- In Dungeons of Dredmor, doors separate every room from every other room. And with the exception of the locked ones you chose to kick down rather than unlock, all of them can be closed again with ease. Since this is a Roguelike game we're talking about, erecting an indestructible barrier between you and your enemies will very often save your life, especially if you encounter a dreaded Monster Zoo.
- This is a key tactic to surviving the levels in the Left 4 Dead series. If you happen to wait too long in the safe house before venturing out into the new area, eventually the AI director will send a horde after you, but they can't get past the door, and lets you kill them off through the barred window. A good wait to rack up kill points for achievements or what-have-you. Elsewhere in the levels, you can close doors to temporarily prevent the zombies from attacking you, but this forces them to either seek out another entrance or eventually break the door down.
- It's not actually used in the game, but many custom maps for Warcraft 3 give you the ability to open and close gates at your convenience.
- Zigzagged in Starcraft II: many natural obstacles are present that can be used this way, but the AI will now attack them as well to open up units for attack. The Terran's Supply Depot building can be sunk into the ground and walked on, allowing for a variant of this trope (if the enemy is stupid enough to let his troops get seperated).
- While the enemies in the isometric Fallout games can open doors, they cannot unlock them. Which means if you are going to be initiating a fight where the enemies are divided into different rooms, you can use your lockpicks to isolate them into neat little cells where you can brutally dispatch them at your leisure. You can also use this with undamaged force fields, and in the first game, at least, to protect your woefully fragile and suicidal companions from powerful enemies.
- In the Retaliation add-on for Mass Effect 3 multiplayer, this option was added to the Firebase Reactor map. The players can now trap enemies inside the eponymous reactor by sealing its doors just as it is about to overheat, killing everyone still inside.
- In FTL: Faster Than Light you can upgrade your ship's doors to be nigh-indestructible. If enemy boarders teleport onto your ship, just lock them out of your vital systems and open all doors between them and the vacuum of space...no more boarders.
- Many creatures in Ancient Domains of Mystery are incapable of opening doors. If the randomly generated dungeon is kind to you, you might find a room that you can run to, close the door, and heal up. Opening up the door again gives you the benefit of fighting the monsters one on one as they come at you. With all the numerous items in the game, sometimes you can come across wands of door summoning, which creates a door for you. Doors can be destroyed, but most monsters don't have the capabilities to do so. Sentient creatures would sooner open the door than destroy it. However, whether enemies can eat through the walls surrounding the door is another matter altogether.
- Quite often in Halo one can back in and back out of the doorway, letting it take the enemies' shots.
- In Metroid, you can often escape enemies chasing you by exiting through the door. They will not follow between rooms but sometimes might hit you a few times inside the door before you get the next one. Backing in-and-out of them is not so useful because walking through the doorway resets each room. The exception, however, is Space Pirates in Zero Mission, who can still follow you from room to room, keeping up the chase.
- The SAX in Fusion will chase the player between rooms as well.
- Empire Of The Overmind. Monsters can open doors but not unlock them. Certain locations have doors which can be closed and locked. If you can lure a monster into the location, you can go outside and close and lock the door, trapping the monster inside the area. One such location has a respawn point where monster re-appear after being killed. If you close and lock the door, you can kill the monsters and they'll respawn inside the room.
- In the arcade game Mappy, your only defense against the cats chasing you is to open and close doors. For some reason, the cats knock themselves out every time they try opening a door, so the player can use doors strategically. Rainbow doors, which only the player and not the cats can open, unleashes a one-time shockwave that picks up any cat in its path and clears them off the screen temporarily.
- Completely averted in Dark Souls. Either the enemies can just walk straight through after you, or it's a boss door and something worse is on the other side. If you're really unlucky, both.
- Resident Evil's early instalments used this, with loading screens between rooms.
- This is a key survival tactic in Amnesia: The Dark Descent. Though the enemies can and will batter the doors down, blocking doors can give you crucial time to escape or find a good hiding place.
- Call of Cthulhu: Dark Corners of the Earth has you do this in an early sequence of the game, desperately locking doors behind you and trying to find a way out.