As far as Old School gaming goes, my cohort Bob and I are strictly amateurs. But between the two of us, we're sitting on a pretty big gob of experience and training in construction design and planning. As such there was one incident during our recent foray into The Castle of the Mad Archmage that piqued our professional interests.
So we’re blundering through the dungeon in our distinctly ignorant fashion when we head down a long passage to the next level that’s labeled “slope 5°.”
Bob: What’s the elevation change between levels?
Me: I think it said 30'
[We do some math: 5° is equal to a 1:9 slope, which means there needs to be 270’ to get down to the next level. Feel free to check our work.]
Bob: Let’s see if this ramp is long enough ... [gleefully counting 10’ squares] ... Oh he’s got it made, well over 300’ here. Even accounting for the landings at the turn and the intersecting corridor.
And, satisfied that our dungeon creator is on top of his game, we move on.
About halfway down the slope there’s a numbered encounter.
Bob: What's that say?
Me: "slope in the corridor is too subtle to be detected under normal circumstances. Dwarves etc. have their normal chance to detect”
Bob: [chuckling] I guess that makes us dwarves.
To put things in perspective for any non-math nerds out there, a 5° slope equals a vertical change of ~1' (rise) for every 9' of horizontal (run). This is significantly steeper than the maximum allowable slope for an
(handicap access) ramp, which is 1:12. Without belaboring the point, a 5° slope is not at all subtle. A consultation with the Joe the Dungeonmaker—isn’t the internet grand?—assures me that it should read 5% slope not 5°. A 5% slope is a much more reasonable 1:20, but no biggie either way, Megadungeon rules apply; if it says it’s too subtle, then so be it. And besides, Bob and I are both looking at the dungeon plans anyway, the cat was already out of the bag. ADA
But then, even if the corridor were perfectly level, the cat would have snuck out in its own surreptitious fashion. There’s something about long, unbroken corridors, you expect to come out of them in a place that is somehow different from the place you just left. Maybe they don't realize that they've left one level and arrived in another but they're expecting a change of one sort or another. Think about going to the zoo: you’re walking along a path with a bunch of savanna animals on either side, then you hit a stretch of path where there are no exhibits for a stretch. Then you find yourself in a new cluster of critters, chances are, these exhibits are somehow different from the savanna you just left. Maybe they’re monkeys--you’ve entered the jungle portion of the zoo. Or maybe the savanna predators are here, isolated from their prey in the previous exhibit. If it was just more gazelles and zebras, you would wonder how they’re different from the critters you left behind, and you might start to think that this zoo needs to diversify its collection.
Just walking that distance gives you time to exit one experience and prepare yourself for something new. It’s the concept behind labyrinths—as opposed to mazes—that the journey itself is transformational. And this works the same in table-top play as it does whether you’re walking through the zoo or traversing the pattern underneath Castle Amber. Even if your players have no idea that they have technically just entered a new dungeon level because they didn’t notice the elevation change, they already know that they left something behind. Walking the length of the passage has provided them a moment of cautious respite, and they’re prepared for something new.
That said, I wouldn’t advise a dungeon designer to redraw his map. Unless the sole purpose of your design subterfuge is to confound the player’s mapmaking efforts—it would be fun to watch the confusion unfold as their map starts bumping into itself in the Southwest quadrant—one needs to not only disguise the elevation change but also hide any other signs of transition as well. Say, if the entire first level, rooms and all, were juuuuuuust so ever slightly sloped—0.5°, 1:100, 1%, choose your labeling convention—toward the northwest,until the party opens a nondescript door off of an unassuming room and, unbeknownst to them—POW!—they’re facing a whole new wandering monster table!