D20 Mechanic: Exploration

This page is an overview and detailed explanation of the exploration system used in T20, a unique subsystem designed by yours truly after many years of thought and design.

Concept

It goes something like this:

Hexes are six miles across, and have one primary terrain type. We'll call this a wheel. And yes, the distance across a hex varies (from face to face, vertex to vertex, vertex to face), but the point here is abstraction, so we don't care. Hexes are a wheel across, done.

Hexes are members of zones, which define potential creature encounters within its constituent hexes.

Hexes have a very important number, Travel Points (TPs). When you enter a hex, it begins at full TP, and as you make exploration checks against the hex, you lower its TPs if you manage to hit the hex.

Hexes have predetermined TP thresholds at which you can leave the hex and move to another.

Hexes have points of interest, which have TP thresholds you must reach before you can find the point of interest. Note that meeting the TP threshold does not mean you automatically find the PoI, just that you might.

Once you have discovered a point of interest, if you return to the hex in the future, you can automatically go there once you reduce the hex's TPs to that PoI's threshold.

Each adventuring turn at the hex level takes a compass, which is about 60 minutes (and is exactly equivalent to five hands); 24 compasses are in a cycle (which is a normal day; and also means that 4 compasses equal a watch).

When traveling in a hex, you may encounter obstacles. These are exploration challenges - cliffs, rivers, and the like. If you defeat the challenge, you continue. If you don't, the hex (probably) regains TPs as you are forced to find another way around (but see the next point).

Some obstacles may interact with the hex in other ways. For instance, a deep chasm that bisects a hex may indicate that, once encountered, the party cannot reduce the hex's TPs until it is defeated.

...and there you have it. That's the core mechanic of how this all goes down.

Thoughts

So this all came to me in a vision, so bear with me. We need to get some thoughts down on paper.

I think the TP threshold to leave a hex is probably going to be half its max TPs. That gives us room for putting things in "out of the way" places in a hex - if you're just moving on through, you're not going to find everything, but you will see a reasonable amount of the hex so that's probably a fair number.

Translating Old Concepts

Remember veer from Journey? That's gone. We're not doing that. Same thing with nodes and subzones and just all that crazy stuff. It was too damn much.

I'm not sure how we'll handle getting lost or turned around... thinking on it, because we've got a lot more mechanics and moving parts, I don't think it actually matters if the players know that they're lost. They can't say "oh, we just turn around" - to leave a hex, you have to reduce its TPs, no questions asked. That represents the idea of figuring out that you're lost, regaining your bearings, and all that jazz.

Notions on Hex Design

So hex design winds up being somewhat related to monster design. Because of that, we need some guidelines.

The big thing to keep in mind here is abstraction, abstraction, abstraction. If at any time you find yourself saying something like, "well, it depends where $FEATURE is in the hex," you are doing it wrong. We want exploration to be fun and engaging, but in order for it to be so there has to be a limit on the information the DM needs to know.

So the idea of a chasm bisecting a hex, preventing you from lowering its TPs at some arbitrary point unless you beat it? Yeah, that's a thing. But now that we've mentioned that...

Problem Case

Hex 0213 has a town on the south side and is bisected east-west by a deep chasm.

If you enter the hex from the S, SE, or SW faces, you'd expect to be able to find the town.

If you enter the hex from the N, NE, or NW faces, you'd expect to not be able to find the town.

How do we resolve this?

Quick answer: hexes are abstract, fool. You can totally divide a hex into conceptually smaller units without having to do all that much more work on the map. Just note that a hex is bisected, and done. This means we do need to track from what direction a party enters a hex, but honestly that does not seem like that much additional overhead to handle this particular conundrum.

Stamina

One thing I do want to implement, because it seems important, is a hit point system to go along with this whole deal. Hit points recover at an astonishingly fast rate, which is fine, but in that design paradigm, we need another resource that depletes slower, or is at least harder to recover.