Game mechanics

opendungeon keeps the dungeon rules consistent across solo and co-op play. Movement, combat rolls, loot, quest state, NPC interactions, and floor events all resolve through the same game rules.

Deterministic state

• Dungeon floors are generated from a seed.
• Legal movement can reveal fog, trigger traps, enter combat, pick up loot, or move the run to a new floor.
• Saves preserve the active run, player stats, inventory, quest state, map discovery, and local metadata.

Seeds

A seed is the number used to build the dungeon. The same seed on the same game version should create the same starting floor shape, room placement, floor modifier, actor placement, and deterministic event placement. Player choices still matter after that: movement order, combat rolls, talent checks, purchases, inventory use, and quest choices can make two runs with the same seed diverge.

Use seeds when you want to:

• Reproduce a bug on the same dungeon.
• Share a co-op lobby where every player starts from the same generated world.
• Replay a challenge and compare decisions.

In hosted multiplayer, the host command owns the seed:

Interaction rules

Players interact with nearby people, notes, doors, loot, stairs, world events, merchants, and combat targets. The engine resolves whether the player is in exploration, dialogue, village, inventory, map, or combat state before accepting an action.

Talent checks

opendungeon uses a tabletop RPG style check for risky loot and events. A talent check rolls a d20, which means a twenty-sided die. The formula is:

The prompted stat matters. A relic inscription can ask for Intelligence, a cache can ask for Dexterity, and a wounded courier can ask for Luck. Rolling 20 is always a dramatic success; rolling 1 is always a failure. Success gives the clean reward, while failure usually still salvages something but adds a cost such as damage, lost focus, or a cursed item. After a check, the toast and log tell you whether it passed, what you received, and to press I to inspect the inventory.

Book and Monstrary

The Book is split by category: story notes, people, and monsters. Monster entries appear when you encounter a creature. Weaknesses are hidden until you hit with the right kind of attack, then the game updates the monster note and shows a weakness toast.

Failure and recovery

The game should expose bad states clearly instead of silently losing progress. Save backups, export commands, and replayable seeds are part of making failures recoverable.

Planned polish

• Better reduced-motion and camera settings.
• More direct diagnostics for blocked multiplayer joins.
• Richer checks around save import, cloud save drift, and GM patch validation.