How to make a co-op dungeon crawler with procedural rooms in TypeScript

Net Forge, the open-source multiplayer browser game engine built for AI coding agents, is published on npm under @netforge with source at github.com/netnetdev/net-forge.

Run npm create netforge@latest my-crypt -- --template dungeon --yes and you have a co-op dungeon crawler: a crypt of ten rooms grown from a seed, up to four players going down room by room, enemies that walk round walls through the doors, an upgrade at every cleared room and a boss in the deepest one. The floor plan is one line of TypeScript, dungeon({ seed, rooms, ... }), and the room logic is a system you can read and change.

npm create netforge@latest my-crypt -- --template dungeon --yes
cd my-crypt
npm run play

--template crawler is accepted as the same template.

#What you get

#1. Start it

npm create netforge@latest my-crypt -- --template dungeon --yes
cd my-crypt
npm run play -- --players 2

#2. Grow a different crypt

import { dungeon } from "@netforge/engine";

const CRYPT = dungeon({ seed: 7, rooms: 14, cell: 28, size: [16, 22], corridor: 6, loops: 1 });

const deepest = CRYPT.boss;
const firstRoom = CRYPT.roomAt(0, 0);
export { CRYPT, deepest, firstRoom };

• seed is any whole number; a different seed is a different floor plan.
• rooms is 3 to 20, the start and boss rooms included. About 10 makes a 6 to 10 minute descent, about 40 seconds a room.
• cell is the room spacing in metres (16 to 32), size the smallest and largest room side, corridor the corridor width (6 lets a boss through), and loops the extra doors that make loops (0 is a pure tree).

Pass field: CRYPT.field to game({...}). CRYPT.boss is the deepest room, CRYPT.rooms gives each room's centre, half sizes, depth and links, and CRYPT.roomAt(x, z) the room holding a point (or -1 in a corridor), so your systems can reason about rooms.

#3. Change what each depth holds

The crawl system reads an ENCOUNTERS table: what a woken room sends, by its depth, for one player. Each extra player adds 35%.

const ENCOUNTERS: readonly (readonly (readonly [string, number])[])[] = [
  [["bone_rattler", 7], ["crypt_bat", 5]],
  [["bone_rattler", 9], ["bone_archer", 3], ["grave_shambler", 2]],
  [["grave_shambler", 3], ["crypt_bat", 9], ["wax_wisp", 4], ["bone_archer", 3]],
];
export { ENCOUNTERS };

Add a new enemy with prefab(...), put it in a row of ENCOUNTERS and in the DEAD list, so a room that still has one standing is not cleared:

import { prefab } from "@netforge/engine";

prefab("ghoul", { model: "style.lowpoly.zombie", health: 30, speed: 3.2, radius: 0.4, damage: 8, ai: "chase", drops: ["wick_small"] });
prefab("bone_archer", { model: "style.lowpoly.skeleton", health: 24, speed: 2.8, ai: "ranged", attack: { damage: 9, range: 10, speed: 7 }, drops: ["wick_small"] });

A ranged enemy shows an aim line before it fires and needs a clear line, so walls are cover.

#4. Test it

npm test

The playtest sends four bots down the crypt and checks that rooms clear, players level and earn rules fire, with no softlock. A crypt whose boss room cannot be reached, or a room that never clears, shows up here.

#How it works

The crawler runs on the same machinery as the survivor-like: auto-firing weapons, level-up cards, co-op downs and revives, bosses with telegraphed attacks. The server steps it at 30 Hz and is authoritative; your character is predicted in the browser. Walls are boxes in the Rapier world for players, and enemies, bolts and spawns are resolved against them, with a flow field (a wider grid for big bodies) guiding enemies round to the doors. A woken room's enemies come in inside that room but off every player's screen. See Simulation and ECS and the dungeon crawler template page.

#Alternatives

• Phaser is a free, open-source 2D framework with WebGL and Canvas rendering. Pick it for a 2D tile-based crawler where you write the generation and the loop yourself.
• Godot has a scene editor and tile tools and exports to the web as WebAssembly with WebGL 2. Pick it when you want to hand-design rooms in an editor.

Pick Net Forge when you want the co-op 3D crawl with procedural rooms, pathing and netcode already working.

#FAQ

#Is the dungeon generated on the server or the client?

Both, from the same spec. dungeon({ seed, ... }) is deterministic, so the server, every client and the playtest grow the same crypt without sending it over the network.

#How do enemies find players behind walls?

They follow a flow field computed over the floor plan, which leads them round to the doors. Big enemies use a wider grid so they do not get stuck in corridors.

#Can I turn permadeath off?

Yes. Set players.downed to allow a free get-up (selfRevives: 1) or a respawn time in seconds.

#How long is a run?

About 40 seconds a room. Ten rooms make a 6 to 10 minute descent.

#Can I hand-design the rooms instead of generating them?

The template grows the crypt from dungeon(...). A game can also declare its own field with walls and floors as boxes, which is how the party template builds its single playroom.