OD&D was brilliant

OD&D gets flak about how hard it was to piece the game rules together from the three booklets. Some have commented that Gary was objectively horrible at writing rules. I think that is total bunk. Yes, OD&D could have been clearer and better organized, but consider that this is the FIRST role playing system ever published. Even today, D&D and many others follow the broad grouping of material.

I find it an amazing achievement. It is incredible how well this has stood the tests of time compared to many other systems. Looking at the original rules, I find it stunning how nearly every page contains useful, actionable information to create and run a campaign, with next to no useless filler. This was a more fully realised system than the basic editions that followed, and in some ways even than todays modern editions. Combined it with best of the four original supplements, this was essentially AD&D. 

Witchking Dragon is licensed under CC-BY 4.0. 

I believe, the reason that OD&D was such a good game is not merely because Gygax was a genius, but also because the game was the result of a two years of play test, and they played every day, sometimes several times. The material in those booklets is the condensed essence of running that campaign in Greyhawk Castle. 

The rules are all over the place because they were never designed. They were grown. They were invented ad hoc during play, as they were needed. Because of this, there are no unifying principles, each subsystem uses a different way to resolve things. But also because of this, you have all those subsystems that you need if you want to run a campaign, from building a keep to naval and aerial combat. (Although the latter is a complicated sub-game reminiscent of a board-game with height counters, written orders, hit locations etc.,  for a rarely needed type of combat, that I wager it might be easier to just wing that with ad-hoc adjucation, as Gary likely did himself. At least it seems to be better than the nigh-unplayable rules from AD&D)

As his player characters became so rich and powerful that the challenges in the dungeon alone did not make for an interesting game any more, they could be lords with their own keeps, lands and armies. So he made rules for that. This was a great solution, because it gave the game another use for treasure. 

He introduced several well-structured forms for adventures, next to the dungeon crawl, there were rules for wilderness exploration ("hexcrawl"), as well as "hex-clearing", i.e. pacifying the wilderness around your keep, to help it prosper.

The 5e rules do not have this worked out, so you get cries that gold is useless in D&D. It's not useless. It's just not useful if your game only is focused on combat simulation and you cannot buy improvement for your characters' prowess in combat after the first few levels. Gary understood this, and found other meaningful ways for you to use your gold, by expanding the scope of the game.

Critique of D&D Design

I certainly will never be nowhere close to Gary in creating a game system. But with hindsight of 40 years of play experience and having played many different systems, I think I can fairly identify a few areas where his judgment was off. 

We were not brought up on D&D, we started with other systems, like DSA, Call of Cthulhu and MERP. With that backgound, even as teenagers, we found the whole D&D experience garish, immature and ridiculous, like a comic book adaption of a novel. I can still recall my reactions of first reading through the (unfortunately 2nd edition) rulebook. The points that I found, and still find, weaknesses were:

• Alignment. This has nothing to do with psychologic foundations of behaviour, nor with the complexity of needs and motivations that drives people to their actions. It's frankly so dumb, Gary had to spend lots and lots of effort in trying to defend it, and considered it a mistake himself to have published it as it was. It is interesting that currently there seems to be a trend to even remove alignment as a given from "evil" races like Orcs, to make the game more inclusive and tolerant. Exabercating the problems with alignment was that he based a lot of spells and abilities on alignment, making it mechanically relevant and hard to ignore.  
• Human-focus with restrictions on classes and maximum level for demihumans. He believed that in a world where demihumans were not so restricted, it would be hard to justify human dominance, and he felt unable to believably describe non-human societies. But elven kindoms abound, from Dragonlance to the Forgotten Realms, as do Dwaven kindoms under the mountains, in lots of campaingns, and nobody does care. He even had humanoid empires of hobgoblins and orcs himself in his World of Greyhawk. The average gamer does not have the same respect for the verisimilitude of the milieu that military history and wargame Gary had. People love to play races that make them feel "special", in 5e Tieflings are one of the most popular choices of all, and the number of renegade good drow played to the image of Drizz't by angst-ridden teenager is legion. You also easily can find reasons to justify human dominance if you want to, for example just assume humans breed much faster than the other races. On a mechanical level, you just need to give humans more flexibilty or some other compensation to make them mechanically as attractive as demihumans, be it skills or feats, as was done in 5e.
• Particularism. He wanted differnt classes and races to feel different. So demihumans could not take just any class. Humans could not dual class. Why? Players love to construct their characters and have "unusual" combinations that belie the archetype and make their characters (and thus, them) feel more special.  And if you do want to play the archetypical gruff dwaven fighter, you still can, and this can be encouraged by pre-made example characters. 3e showed that there is no harm to allow any combination of class and race, and no harm to allow anyone to take levels in any class to create dual or even triple or quadruple class characters -- you paid the price of going broad by not getting access to the higher class-level related abilities and feats that you got from staying focused. (The only problem was that many classes were front loaded with a lot of key abilities on level one, but once you understand that, you can address it in class design). Getting rid of these restricitions also simplified things. 
• Different experience level progression ladders by class, and in OD&D even different listed top levels by class. Unneccesarily complicated. Even with that wizards were very weak in the beginning, and uber-powerful towards the end, in keeping with Conan and Dying Earth, so what was the point? It may have been because he allocated XP to wizards for spells cast, and with more and more slots, the number of XP gained that way per day would grow non-linearly, while fighters had no such method. But that could have been simply fixed by not allocating XP in such a fine grained manner, just give group based XP as is done today. Again, I think his repect for the "reality" of the game world got the better of him here.   
• No core mechanics. For the reasons above, every system used differnt dice, tables, and resolution, sometimes you have to roll over or high, sometimes under or low to get a good outcome, sometimes percentile dice are used, sometimes d20, sometimes d6, d12, 2d6, 2d4 etc. 3rd Edition showed how this can all be cleaned up with a core mechanic of d20 rolls over target, high rolls being good. 
• Attributes. While his seletion was a good as any, he made no good use of these attribute values initially. Also it again made no sense why only fighters would get a given benefit from say, high strength - even if you could justify it, it made things unneccesarily complicated, as 3e who treated all the same would show. In particular the ridiculous Stength 18/% for fighters. I get it that he wanted to strenghten fighters so they would hit better and deal more damage and be stronger than other humans that lacked training. But why not just give fighters a +1 bonus then on Strength (or something like that), even if that brought them out of the normal range of untrained humans? Also, each attribute gave benefits at different cutoffs. Again, 3e cleaned all that up with standard boni and mali for a given value, no matter what attribute.
• Saving throws by souce class with own table. Firstly, this did not extend well as new monsters and effects were introduced, but that is a minor quibble, you can state that the slime lords touch that liquefies flesh needs a save against petrifiction as easily as you can say it needs a Con save. However, this again is just unneccesary extra ballast and yet another table to look up. It worked great for other systems like DSA or 5e to just base the saves on the character attributes, and if you wanted class or race to count, you could give certain saves a bonus based on those. 
• Rules that are nonsensical by in-world logic just to make life difficult for PCs. This includes rules that treat monsters differently from PCs:
• Dungeon doors, that never are stuck for monsters, but by default are stuck for PCs and need to be forced open. There is absolutely no logic in this -- maybe this could happen for a single door, that needs a certain "knack" (slight lifting or such) to be openend, but certainly not all of them. 
• Monsters being able to see in the dark, unless they serve a PC. Again, there is no logic at all in this. Either the creature does have "infravision" as darkvision was called back then, or not. Both of these make no sense in in-game logic and are purely "gamey" treatments to give an advantage to monsters over PCs that disrupt the suspension of disbelief.
• Scrolls "vanishing" over time if they are not cursed and not read, to ensure scrolls are read and cursed scrolls get triggered.
• 
  

There are also some design decisions that he later admitted were suboptimal choices for roleplaying in general, but that were in particular well matched to playing archetypcial fantasy tropes in a dungeon envrionment of ever-escalating danger and deadliness of monsters. 

• Low-Level deadliness. Gaining experience and improving your character towards the next level was a core driver that made the game addictive, and likely a great part of its success. It still is used today by games everywhere, wether on computers or in paper RPGs, so it is hard to call levels per se a design mistake. However the vunerability of first level characters was too high. You could die from a single hit. Sure, it was not as time consuming back then to make up a character. Still it is a bad beginner experience to create a character just to see him being wasted by an unlucky roll. Gary in later years started characters on level 2 or even level 3 to adjust for this. 
• Classes. While this makes it simple to play a given archetype, non-cookie cutter character concepts are either impossible to represent with such a system, or unnaturally complicated to approximate by dual- or multiclassing, which also was not generally allowed in original D&D and AD&D. He himself admitted, that an approach based on bundles of abilities would be a better system. This is not so much an issue when you play this the first time, but it will become an issue once you want to be a bit more creative about your character. 
• Lack of skills. You can get around this by assuming certain classes have certain skills or abilities, and roll against the most relevant character attribute, as he did in his home game, but this was nowhere formalized part of the rules. He later admitted that using skills, and defining archetypes by bundles of skills was a better approach to character concepts. 

In general, he had a hard time to let go of his choices, like d100 on strength for fighters, different XP ladders for different classes. 5e's approach to saving throws takes less mental baggage, less tables to look stuff up. But it still is amazing how perfect his original system was. 

Lastly there are w few design decisions that were changed later over time, to take the edge off, and that I am not sure about if they were mistakes or not:

• Save or die rolls. I'm not sure on these any more. I used to hate them, it always felt unfair that your character carefully played over months and years should perish to a random unlucky roll. Now I think these capture some of the excitement and danger by stripping away the saftey padding hp provide at higher levels, and characters should have access to magic like hold poison, cure poison, stone to flesh, or gold to pay for them. In 5e, poison and petrification monsters lose a lot of their terror and become just another opponent.
• Level Drain. I loved that as a GM, and players obviously hated it. I think the dread of losing levels and permanently setting the character back without it outright, was a great way to make greater undead terrifying. And in the very simple OD&D, losing a level was not that hard to note on your sheet. The probelm was that administrative overhead of this, once the rules got more complex in AD&D and you had to undo all the additional abilities you gained with levels. There are complications -- how many hp would you lose? Did you need to record how many you last gained, or just roll again? In later editions, less onerous approaches like lowering the hit point maximum or attributes were taken, which were also less terrifying, because they did not lower your overall fighting ability -- a mage with less hp still could cast all his spells, and they could be reverted with curative magic. In 5e, this again has been furhter nerfed and padded to a mere nuisance, with characters being able to recover after just a night's sleep. I think a practical approach would be something like petrification, a permanent effect that can be undone with some spell that has a costly material component. 

On the rate of Leveling

There are two rates of leveling: first, how long do you have to play, to gain a level. Second, how long does it take in-game for your character to gain a level. 

In-game

How fast you gain experience in-game obviously depends on how your character spends his time. If he is engaged in uneventful overland trecks, weeks of downtime to craft items, or takes a break just relaxing and waiting, little experience will be gained, and it can take months or years. So the real question there becomes, how fast in-game can the character gain levels when engaged in the most strenuous activity, making most of every available resource or minute in an effort to gain exprience. 

"Experience" is licensed under CC-BY 4.0. 

In 5e it takes a little more than a month of in-game time to go from level one to level twenty. You'll spend approximately two days of in-game time on each character level, before moving on to the next one. Of course, with travel, downtime and so on, it may take longer, maybe two or three months of game time. But still, no years of heroics to become a world-dominating legend. 

In D&D 5e the standard experience rules that assign experience primarily for killing monsters, that means dangerous adventures with as many combat encounters as you can stomach, if you follow the DMG guidance on encounters per day and the XP per encounter, you get this table. 

Table 1: Experience and level achieved after number of days adventuring

Day    XP    Level

1 300         2
2 900         3
3 2,100 3
4 3,300 4
5 5,000 4
6 6,700 5
7 10,200 5
8 13,700 5
9 17,200 6
10 21,200 6
11 25,200 7
12 30,200 7
13 35,200 8
14 41,200 8
15 47,200 8
16 53,200 9
17 60,700 9
18 68,200 10
19 77,200 10
20 86,200 11
21 96,700 11
22 107,200 12
23 118,700 12
24 130,200 13
25 143,700 14
26 158,700 14
27 173,700 15
28 191,700 15
29 209,700 16
30 229,700 17
31 254,700 17
32 279,700 18
33 306,700 19
34 336,700 19
35 366,700 20

As a pure spell caster, you gain two new spells every spell level. When you gain a new spells up to character level 5 you get two slots to cast it, after that only one; followed by an extra slot on the next character level, up to character level 10. That means, when spending typically two days on each level,  in the lower levels you have 2, 2, 3, 3 = 10 shots to cast your new spells, before moving to the next spell level. In the mid levels you have 1, 1, 2, 2 = 6 shots. In the higher levels 1, 1, 1, 1 = 4 shots. Starting in the mid-levels, you get to cast each of your new spells maybe 3 times before moving on, in the high levels only twice. And this assumes that you do not find any additional spells adventuring on scrolls or from a captured spell books. If you find just a single new spell per level, then you will barely be able to cast each spell once before moving on mid-levels, and not even that in high levels.

This feels a bit fast for my taste. You do not really get to explore your newfound abilities, already you are on to the next shiny toy. If the progression was slower, maybe even by just a day or two per level, you could explore the spells more, get used to them. Of course, you still can use them later on, when you are on a higher level. But it feels a bit anticlimatic, if you finally get to polymorph someone on level nine. This would speak for slower experience. However, other classes gain less new features per level than spell casters, and for them the current rate may be just fine. 

In real-world time

How long should it take you to gain a level in play time? My answer is between six and eight evening game sessions. 

I think this is more important than how long it takes in-game, if you assume the main goal is to play a full campaign. The three important ingredients are and what level you need to reach, how long a campaign can run if you intend to finish it, and how often and long you get to play. 

In Gygax' original campaign old veterans had PCs with levels in the teens after about 10 years of play. [#8360]. 

That seems rough. With moving around for education and jobs, getting kids, changing life priorities and interests, any single game that requires you to contiuously commit yourself over 10 years is likely to be abandoned. Two years for a campaign looks doable. Keeping it up for four years is already much harder. 

A normal person for whom RPG is a pastime among others and not the center of their life will not play 7 days a week, as Gary did. We are playing about once per week for three to four hours of real time, and that is the same rate I have experienced in other groups, too. One evening a week is as good a rate as you can expect for a hobby, maybe dropping a few weeks each year to vacations. With busy jobs and kids and family, once a fortnight may be more realistic. 

So you are looking at a bit under 50 sessions a year, and you should be able to finish a campaign within two years or so to achieve closure. Campaigns do not have to go to level 20, in fact very few do or did, level 12-13 is entirely fine and may be preferrable. Even in Gary's campaign, nearly all players retired their characters around there. For this, you would need to gain about six levels a year, one level every two months or seven to eight sessions. 

Gary Gygax said I think that 52 sessions to reach 10th level is about right if the time per session is about four hours. [#5188], which is in the same ballpark.  This would come to about six sessions per level, that being action-packed sessions with theatre of the mind. With weekly play, it would take a year. He has other estimates that made it two years. 

We took nearly two years to get to level 10, but we only played biweekly in the first year, and we often play only three hours effectively, after kids are in bed starting around 9 pm, and ending around midnight with work the next day.  Our DM also is slow in adjucating, taking long time to look up adventure text, not feeling at ease with inventing on the spot to keep things moving, taking a lot of time to count squares in battle sitations. We have too many lengthy rules discussions, and virtual tabletop technical issues tend to slow things down further. So this seems to match the above rate given the extra impediments.

I expect it will take another two years to get to level twenty, if we can stick with it -- there is a bit of fatigue showing. 

Level 20

We never made it all the way to level twenty, and it would be a cool item for the bucket list to have played one character or campaign all the way through. All earlier campaigns and groups faltered after about 10 or so levels, the longest one went to level 14. 

Getting to level 20 is hard in older editions of D&D, because it took forever to get to the higher levels XP wise, but in all editions, because there are not a lot of good adventures for high level play, campaing arcs tend to end at level twelve or so, and the game also is not designed for high level play and less fun there.

Leveling In OD&D

In Gary's campaign, where the same character was played weekly, sometimes more often than that.

Good players could manage to gain low levels for their PC in a half-dozen or so adventures. Poor ones, those just goofing around couldn't manage that in a dozen adventures. [35] 

By the time AD&D was being played, all that had been ironed out, and the good players were still gaining a level for their PCs every couple of months until mid-level, say around 8th. [35]

The number of XPs given to rise a level was initially intuitive, later on based on the play of my campaign group. I think that 52 sessions to reach 10th level is about right if the time per session is about four hours. Longer sessions would reduce the number accordingly. #5188

A group playing once a week for three to four hours, playing well as a team, should see a 1st level PC that make about one level every three or four months on average. So that should get the typical party member to 9th level at the end of two or three years as you suggest. [35]

Its ambiguous what adventures relates to in the first sentence - game sessions? There were no adventure modules per se in the early days, only forays into the dungeon. This interpretation would mean six to twelve sessions per level, six with competent play. The third statements indicates gaining a level on average every six sessions (nine leves over 52 sessions), eight or more i.e. "a couple of months" towards the end, so maybe around four in the beginning. The fourth statement assumes much slower progression, one level per twelve or more slightly shorter sessions. 

The old veterans had PCs with levels in the teens after about 10 years of play.  [#8360]

A 15th level PC in AD&D requires years of gaming, and when arriving at thay level the character is generally retired. In new D&D arriving at that level takes a mere few months, and that PC is nothing compared to the half-dragon/half-vampire multi-prestige class one that the kid next door stomps around the campaign world with #3850

After name levels, this slowed down significantly, taking about two more years per level if you reached 15th after 10 years. This slowdown mirrors my own experience from second edition, and may also reflect that the high level PCs were played much less regularly. 

In-game time to level in OD&D

If play was intensive dungeon crawling, the 52 play sessions might take up only a few weeks of game time, with several adventure sessions being the continuation of a single day of delving. Also, when magically sent to another location time was generally different, and one reappeared in the original place with only a fraction of subjective time while away having passed in the home universe.  #5189

At  low levels if you gain ten levels in the span of a year of real-time sessions equaling "a few weeks" of dungeoneering game time, then your character would gain a level every two to three days of game time, same as in fifth edition. If it takes you two years and twice as many sessions to get to level 9, these 52 sessions and "few weeks" would only get you to leve five, and it would take you four or five days in game to level, half as fast as in fifth edition. 

Outdoor adventures might consume months of game time, of course. The latter posed a problem for players used to adventuring as a group when they were not with the others on an outdoor foray, so the regulars would often seek their fellows on such jouneys. To answer in general, the time span for 52 adventure sessions was generally anywhere from as many weeks to two years or longer. #5189

Also note that in OD&D, XP and leveling was defined much more by the treasure found, than by the monsters defeated. So if you made the mistake to hand out a huge treasure that was inapropriate, this could wreck havoc with accelerated progression. 

I am not particularly find of playing one game session and going up a level. That hardly qualifies as "eaned," to my way of thinking. However, if the campaign is set up for very high level play, such increase might be warranted. I did play in and enjoyed that sort of gaming with my French fellows, Francois Froideval being the DM. (My 12th level fighter was a mere peon, akin to a low-level PC, in that campaign.) [35]

I don't think you should ever allow a PC to gain more than one level from an adventure success. #1683

On Slanting Passages

Slighlty down-slanting passages that would transport you from one level to the next without you noticing were one of Gary Gygax's favourite deceptions in dungeon design. Going to a lower level meant much more dangerous encounters, doing so unbeknownst not only messed up mapping but could be quite deadly. An insidious trick. 

It was so dangerous, Dwarves even had a special sense to detect this, and players tried ploys like spilling water on the floor, which Gary soon ruled was running into cracks in the floor to block it. Rolling marbles would also work, but I am sure Gary would have ruled the floor was too rough for it.

Sloping Corridor is licensed under CC-BY 4.0. 

The problem with sloping passages is: they do not work. I mean, physically. Even without water or marbles. Gary never did the math on this it seems. By accounts from building standards, a slope of even 1.5% is quite noticable by anyone, normal humans, no dwaven senses needed. Let's give the idea the benefit of the doubt and assume you can get away with 2% slope unnoticed. 

In Greyhawk Castle, each level is likely about 50 feet deep. That means, to go from one level to the next without noticing, you need a corridor that is 2,500 feet or nearly half a mile long. (2% means 2 feet down per 100 feet , or 1 foot down per 50 feet, so to go down 50 feet you need 50 x 50 feet = 2,500 feet of corridor).

The typical size of a level in Castle Greyhawk, along the long edge of the page is about 50 squares. This naturally follows from 4 to 5 lines per inch paper and the page size of a letter page. At 10 feet per square that means 500 feet for the long edge of the map. We have the maps of level 1 and 3 to count it off, too.  

To go down one single level unnoticed by sloping passage you would need to go back and forth the entire length of the level five times. None of the corridors in Gary's maps are that long. Even if they were, it would be highly suspect to walk along a corridor hundreds of feet, and defeat the purpose of unknowingly passing from one level to the other. 

And all of that is assuming you can get away with 2% incline, which you likely cannot. Nevermind going down two levels, that would be a mile long trip. If you used a more realistically unnoticable slope of 1%, we are talking about a mile for a single level.  

Even if you keep 2% and cram the levels tight on top of each other, say 20 feet deep with no high ceilings, you still look at two trips along the entire length of the map, and it would make use pit traps impractical, or at least you need to check if they drop you into a room or corridor on the next level. 

You would need magical distance distortion effects to justify the tactic. At that point, you can just as well use teleporters along indentically looking corridors. Sorry, Gary.

P.S. Someone who also cought this fallacy asked Gary about it on a forum. Gary was obstinate, defending himself thus:

In a dungeon all of the passageways might be inclined up or down. If one can't accept something so petty as an undetected slope in a passageway, how can flying, fire-breathing dragons and all the rest of what makes the genre what is is by justified? A whole lot of suspension of disbelief is mandatory to play FRPGs... [35]

I do not buy that argument. There is a difference to suspend disbelief for accepting magic that escapes physical logic, and enables dragons to breathe fire and wizards to fly and turn invisible. Yes, there could have magically enchanted corridors to achieve this. But the fundamental physics of the world are those of ours, and with those, this will not work. 

Mundane Detail

A richer understanding of the mundane

Under the tag "mundane detail" I write entries that delve deeper into mundane areas, which normally are not the focus of the PCs interest, but help to make the world more believable. Because such mundane detail existed in the real world's middle ages, often these are articles reflect how things were done in the real world medieval period, to then adapt and use them for the game.

• The well stocked larder
• Barrels

How to avoid the need for mundane detail

The principle of description economy tells us to leave out anything that you can make up on the spot. Such mundane detail not only does not add, it makes it hard to find the information that is actually important, and hence detracts from the value of the manuscript as a play aid. 

A better solution than describing mundane rooms in detail in any given adventure is to have a list of things that helps the GM to come up with different, specific descriptions for such rooms in the moment. Gary Gygax did realize that when he created  Appendix I: Dungeon Dressing, which provided exactly such lists: items, sounds and features that could be found in "empty" dungeon rooms, and more specifically, rooms such as chapels, laboratories, libraries, living quarters and torture chambers. Most of these lists even made it unchanged to Appendix A of 5e. 

Even though he provided numbers for each item, to allow random picks, his advise for each of these tables was to "Select from the above list. Use random determination only to round out or fill in.", or a variation of this wording. Their purpose is to provide a fuse for the DM's imagination.

For these lists to be useful, they need to be densely written and quickly looked up -- ideally they fit on a DM screen pane, if you use a DM screen. I think the ability to post such quick look-up aids to jog imagination is the main value of a DM screen, much more so than any use in hiding die rolls. 

Why is there so much mundane detail in published adventures?

Adventures often waste a lot of text on describing the contents of mundane rooms. Why do that, when just labeling the room as "kitchen" or "well-stocked larder" and common sense should be sufficient for the DM to describe what the room contains? 

First - there is actually something special going on. If there is a giant slug in the basement, the PCs might think of getting hold of a sack of salt to damage it. Does the larder have salt, and if so how much? The DM can make this up on the fly -- if the description was "well stocked larder", I would venture there is at least a medium sized sack of salt, enough for one meaningful attack comparable to alchemist fire. But if there is a whole barrel of salt, because the writer thought of the tactic, then this should be pointed out in the adventure text.

Second, it is harder than one thinks to come up with colorful descriptions of such mundane rooms on the fly, without falling into the same, repetitive stereotypes and patterns, and the writer wants to provide help.

Third, if the DM just gives a bland description of a kitchen, without calling out anything specific or unusual, this may let the players conclude that there is nothing going on there and move on. That is not necessarily bad, after all, there is nothing going on there, and players will just waste game time searching a mundane room for hidden secrets that are not there. The problem is the flip-side of this: as soon as there is a specific description, there will be something special, which acts as a filter for the players their PCs would not be aware about, and robs the game of verisimilitude. To avoid this, provide some weird details also to mundane rooms.

Fourth, the writer of the adventure did not think about how to make his design useful in play. They are the kind of writer who likes writing, and likely also write paragraphs about what the room used to contain that players will never learn about and that are irrelevant to the exploration at hand.

Colors, Energy types, Elements & Types of Magic

Delta has an interesting article about the elemental damage types in OD&D and their associated colors.

OD&D ostentatively only had four damage types accessible to players: fire, cold, lightning and physical (weapons). Poison was just save or die. Monsters had more: green dragons did chlorine gas damage instead of poison (essentially acid), black dragons acid damage. And even players also could deal "air" damage through summoned air elementals, or "earth" damage through summoned earth elementals. Later in Greyhawk players got acid damage with Melf's Acid Arrow. Magic Missile from Greyhawk originally was untyped.

I find it amusing that OD&D found space for a table of +/- 1 modifiers to hit and damage against dragons by damage type, which may tell us a bit more about what opposes what, but which seems an odd choice given the modifiers are so small. (Aside: I also find the subdual rules mystifying -- why would anyone ever not opt for subdual? You very likely end the fight quicker than if you have to kill the dragon by removing all of his hp, plus you get your own personal dragon in the deal, too. There seems to be no downside for subdual?)

Ancient or medieval wrong models of how the world is composed had four to five substances or qualities. Aristotle had hot, cold, wet and dry that create the four elements we typically use, hot/dry = fire, hot/wet = air, cold/dry= earth and cold/wet=water. These conveniently also can be grouped into oppsing pairs and connected up with the elemental damage types:

Fire - Fire

Water - Cold

Earth - Acid

Air - Lightning

Chinese philosphy had five: Fire Water, Wood, Metal, Earth. Air is missing, and as this is not the western model D&D used, there is no easy damage mapping.

In later editions, all the different bludgeoning attacks no matter what caused them were just physical bludgeoning damage. Magic Missile was redefined to "force" damage. Nowadays there is a much larger list of standard damage types in the game. If you take resistances and immunities into account, anything can be a damage type. Some devils can only be hit by magic or cold iron? Now iron is a type.  A fey is immune to wooden weapons? Now wood is a type. Even without such shenanigans, the list of types now is quite long. For many of them, it would be difficult to assign an "element" type for the kinds of elements that have been thought of as building blocks in ancient systems.

1. Physical (Slashing/Piercing/Bludgeoning)
2. Silver (Slashing/Piercing/Bludgeoning)
3. Magical (Slashing/Piercing/Bludgeoning)
4. Poison - Wood
5. Fire - Fire
6. Lightning - Metal
7. Cold - Water
8. Acid - Earth
9. Thunder - Air
10. Psychic - Soul
11. Necrotic - Undead
12. Radiant - Holy
13. Force - Magic

Humans can only think about five to seven things at the same time. Better five than seven. So any list that long is not accessible to a nice mental model any more. 

Magic Colorbook

Magic: the Gathering used a brilliant classification scheme, by arranging five classes in a circle, and giving each a "color" of Magic. By giving primacy to the color, each color could have a portfolio that went wider than just an elemental type:

Red - Fire, Earth, Chaos, Emotion - typical creatures goblins, giants, dragons

Green - Wood, Growth, Nature, Animals - typical creatures elves, wurms, hydra

White - Order, Healing, Altruism, Good - typcial creaturs humans, pegasi, angels

Blue - Air, Water, Thought, Time - tyical creatures merfolk, djinni, sphinxes

Black - Death, Undead, Egotism, Evil - typcial creatures zombies, vampires, demons

Garfield brilliantly packed all the standard elements into just two of the colors, so there was a lot of room for other colors to comprehensively capture classes of magic. By having just five in a circle, he had a structure where each color had to allied and two enemy colors.

I think this is a wonderful classification, more inspiring than the "Schools of Magic" in D&D, wich have no useful structure among themselves.

Energy Colorbook

For mapping energy types to colors, there can be no right system, as all of this is based on unscientific intuition and association. That said, here are some options:

Type        #1        #2        #3              #4        #5

Fire          red       red      red             red        red

Water       blue     white   dark blue  green    blue

Air           white   blue     light blue   white      yellow

Earth        black   black   green        black    green

Scheme #1 opposing fire/water get a chromatic color pair, the opposing air/earth the achromatic black and white. Blue is most intuitively associated with water, while "no color" white is most intuitively associated with "no color" air. Of course, both air and water are transparent. These colors do not fully fit dragon colors. Blue dragons breathe air-borne lightning, not white ones, and white ones breathe watery cold, not blue ones.  

Scheme #2 fixes this and uses the color of the dragon that breathes the element. This swaps white and blue from scheme #1. Think of white ice as a form of water to justify the color over blue, and blue sky for the color of air and lightning. I think this is the most "D&D" color scheme, and is what I would use.

Scheme #3 is from Gary, inspired by the lighter blue skye and darker blue ocean, and is all chromatic, no black or white, but I think it is crap. Two shades of the same color? C'mon.

Scheme #4 is from Delta and uses green for the deep watery ocean, but green dragons do not breathe cold, so that does not fix the dragon energy type issue; you could replace air with blue now that blue is freed up, but that has the uglyness that we then have 3 chromatic colors and black.

Scheme #5, I'll call it the Google scheme, only has chromatic colors. I think if you stick to the elements for color, and forget about the dragon colors, this is the most natural one. Yellow is the color of lightning  in childrens paintings (although in reality it is white) and thus fits to air/lightning. 

Color Wheels

In color schemes out of the context of fantasy, the Natural Color System identifies Red, Green, Blue, Yellow, and Black, White as the six psychologically primary colors. So the four Google colors plus black and white. Which actually matches the OD&D dragon colors, if you take yellow for the golden dragon. 

In classical color circles, the primary color triad is red, blue, yellow, with the secondary colors between them green, orange, violet, and another six tertiary colors between those six. These choices are arbitrary convention of course, you could pick any three equidistant spots on a color circe as your basis. 

What about other damage types? Logical color mapping quickly breaks down, as there are too many types. You can see a possible mapping in the colored list of the energy types, above.