Some thoughts on key/switch usage in Doom

[Logamuffin]

INTRODUCTION

 

I’ve been thinking about how Doom maps use keys/switches for progression for a while, and I sort of just wanted to let all my thoughts out on the subject. Thus this post. Let me explain:

 

THE THREE KEY FORMULA

 

Ok, so I was playing Nostalgia 2, the new megawad from myolden and the reason I bring it up is as an example of how it uses keys. In particular, most of the maps’ progressions follow what I like to call the “Three-Key Formula”:

 

Get red key > Open red door > Get blue key > Open blue door > Get yellow key > Exit

 

This is the most common way I’ve seen keys used in Doom mapping, and it makes sense why.  Keys are designed so that players can feel like they’re progressing through the level instead of just killing a bunch of monsters then leaving, while also extending levels by adding another objective for players to complete. So using this formula where each key opens another area that leads to the next key, is the most linear and (as I would argue) least interesting way to route keys in your Doom maps. That’s why I brought up Nostalgia 2 specifically because after 20 maps of the above progression it really started to grind my gears. There’s nothing wrong with using the Three-Key Formula, it’s a tried and true classic for a reason. I just think there are more interesting ways to use keys in your maps. For example:

 

THREE KEYS (Non-Linear)

 

This one would be something like:

 

Red key > Blue key > Yellow key > Use all to open exit

 

The best example for a map like this is Doom 2’s The Citadel, in which you must wander around the map collecting all the keys. And therein lies the problem with this design because the more nonlinear a map is, the harder it’s going to be to lead players to required objectives. So you can end up running around like a chicken with its head cut off trying to figure out what you need to do. There are several solutions for this, one of them being just good level design: Make it clear where the keys are and where the player needs to go to get them, and let them go from there. Or you can increase the linearity of the map by making it so that one key leads to another naturally.

 

Whatever the case, I’ll say that this type of non-linear key usage is my favorite type and I tend to love maps that do this (Valiant’s Engineering Disaster to name another example). But I understand why it’s a bit less common then the Three-Key Formula because it’s a lot harder to get right, as you have to account for the multiple paths players could potentially go down and balance your map accordingly.

 

OTHER KEY ROUTES 

 

Of course there are also other ways to use keys that don’t involve all 3. One example is optional/secret keys like the black key in Swim With The Whales’ titular map. Or you can do a hybrid linear and nonlinear map, for example. Something like: 

 

Red key > Red door > Blue key > Yellow key > Exit

 

Or you can use less than 3 keys, but I think I’ve said all I have to say about keys. Let’s move on.

 

SWITCHES AND SWITCH HUNTING

 

Unlike keys, where you can only have a limited amount, you can have as many switches as you want in a map. However, this comes with a drawback because with many switches in a map, it becomes much harder to tell what switch does what. This can lead to maps that overuse switches to suffer from (as MtPain27 termed it): “What the heck did that switch do?” syndrome. This is much more common a problem in older maps, though frustratingly some newer maps do this too. Another issue is that hitting switches is much more repetitive an objective then gathering keys. If we map out a diagram for it, it’d be like.

 

Hit switch > Opens new door > Hit switch > Opens new door > Hit switch > Opens new door ……………. Hit switch > Exit

 

Though switches are also more versatile in what they can do than keys, so this repetitive process rarely matters. However it can get tedious in a long switch hunting map like, AV’s Misri Halek which has tons of switches you need to flip to progress and it can start to get irritating over the course of the levels long runtime (The main reason I don’t really care for Misri Halek. I know, sue me.) However the upside to this type of switch hunt is that it allows for much more control over where the player can go compared to keys, and that can be useful for balancing, pacing, etc.

 

SWITCH HUNTS (Non-Linear)

 

There are very few of these types of maps but I thought I should bring them up anyways. The progression would be something like: 

 

Switch > Switch > Switch > Switch ….. > Exit

 

The immediate problem with this is obvious because finding 3 keys in some non-linear maps can already have you lost easily. So having you track down a bunch of switches is going to have a much worse effect. An example of this type of map is Ogdoad from Epic 2, where after the key progression is over, you must track down 8 switches scattered across the map to be able to exit. If that sounds bad, that’s because it is…

 

But one way I’ve seen this problem solved is from a map I adore called City Heat from Community Chest 2. In this map, you have to hit 9 switches to be able to exit the level. However each switch is in a numbered building and the map tracks your progress by letting you know what switches you have and haven’t hit. This allows for much more bearable non-linear switch bunting gameplay, and I wish more maps would take up this design.

 

CONCLUSION

 

Ok so this is already long, but I of course have to mention that most Doom maps of course use a combination of keys and switches for variety’s sake and there are more design quirks and theories you can come up with when you consider this, but that’ll be an essay for another time. I hope this was helpful or interesting to… someone. Maybe try to use some of these non-linear/non-traditional progressions in some of your maps!

 

 

Edited March 18, 2024 by Logamuffin

[DoomGappy]

Great topic. I like the way you talked about the keys and progression. I thought about two cases that you missed, though: 1 - More than one key of the same color and 2 - Keys in different places depending on difficulty. I don't know many maps or any good examples that do this. I'm doing numebr 1 for my map for NOVA IV, which will have two routes, and the way you navigate the map and the order you pick the keys will change the paths you will travel. I think this can guarantee at least a second playthrough of my map and it mught be a cool little thing. I talked about it on a thread some time ago but don't remember which.

[Shepardus]

Nice writeup! I'll add some of my own thoughts on keys:

• You can have more than one of a given key type, giving players the freedom to choose which one they get. The first example that comes to my mind is DBP50 MAP08 ("Gather 3 of many keys, and you may leave town as you please.")
• You can have keys without actually using them with keyed doors. This can be for technical reasons, like if you can't do something with a keyed door but can with a walkover linedef around the key (e.g. the yellow key in 5till L1 Complex), or if you just want to use keys as objective markers (the yellow skulls in Going Down MAP23, Demonology, come to mind).
• One of my favorite uses of a key is in E1M3, where the yellow key is easy to find, but the door it opens is within a secret. Gives the player curiosity to explore more and figure out what the key is for, back before source ports readily showed the secret count to players.
• One thing I wish Doom had but doesn't is the notion of a consumable key, i.e. a key that is used up when you open a door with it, possibly with the ability to carry multiple keys at once. There's many things you would be able to do with that, like having unlockable treasure chests/supply closets and a simple currency system. Heretic, Hexen, and Strife even have inventory systems, yet they don't have this sort of thing. I suppose with Boom voodoo scripting you could keep a counter as players walk over linedefs, and with ZDoom you can implement whatever items you like, but with vanilla you don't have many options. Bury My Heart Knee Deep has an interesting approach that uses rockets as currency, though having to dedicate the rocket launcher to that function is quite limiting.

19 minutes ago, DoomGappy said:

2 - Keys in different places depending on difficulty. I don't know many maps or any good examples that do this.

That's a good one too. The classic examples are in E3M6 and Doom II MAP06, the blue key in both cases. Planisphere II is another example, with the keys being (ostensibly) easier to find on lower skill levels. I'm sure there are other examples but I can't remember them off the top of my head.

Edited March 19, 2024 by Shepardus

[Andromeda]

23 hours ago, Shepardus said:

The classic examples are in E3M6 and Doom II MAP06, the blue key in both cases. Planisphere II is another example, with the keys being (ostensibly) easier to find on lower skill levels. I'm sure there are other examples but I can't remember them off the top of my head.

Perdition's Gate MAP01 as well.

[Enzo Carozza]

21 minutes ago, Andromeda said:

Perdition's Gate MAP01 as well.

> mentions Perdition's Gate
> automatic like on post :333