What the GM Makes

The shortest way to understand Tesserae's design is this: the Game Master invents nothing structural.

It does not build regions, choose terrain, place creatures, or decide what is on a tile. All of that is authored in files before the session opens. What the GM contributes is narration, adjudication of rolls, and the bookkeeping of three fields.

What the GM may write

On a region:

• a tile's explored, set true on arrival
• a tile's cleared, set true when its creature is dead and its discovery is spent
• currentTileId, the tile the traveller is standing on

On a character: hp, gold, equipment, inventory.

That is the complete list. Everything else is authored content, and the GM instructions say so in language that leaves no room to negotiate.

Why it is drawn this tight

Two reasons, and the second is the one that bites.

Art is attached to coordinates. Each region's map is authored hex by hex, keyed to each tile's q and r. A layout the GM invented would have no art at all, and a tile it moved would show the wrong ground. There is no way to repair that from inside a session.

Geometry is not intuitive. The geometry block on a region turns axial coordinates into positions on the artwork. Four numbers. A GM that recalculates them lands tokens between hexes rather than on them — see Drawing the Map, which exists mostly to explain why nobody should be doing that arithmetic by hand.

Never store what can be computed

The region computes _tokenX, _tokenY, _creatureTokenX, _creatureTokenY, _exploredCount, _progressLabel and _currentTile. The character computes its stats, defense, damage and max HP.

Computed fields are never stored in file content and writing one is silently discarded. When you add a field, classify it first: is it stored state, a definition belonging on a referenced type, a computed projection, or presentation? Presentation — labels, glyphs, formatted strings — is the layout's job and never a schema field.

Where the seams are

Tesserae grew out of a dungeon crawler, and a few fields are still wearing their old clothes. Items and creatures carry minDepth, which meant something when there were floors and depth bands. There is no depth here. The GM instructions tell the GM to ignore it. Leave it or strip it, but do not build anything new on it.