Crescent

2026 · a game engine a model can pilot

I want a world where people can speak a game into existence. You sit down with a model, you talk about the game you want, and the game comes into being. Crescent is the tooling to get there.

01

A tree is a page of text

A tree can be described analytically, and there are good tools that do it. They are native applications, which a model can't get into. So this one is a page of text. Each sheet below was written by a small language model that had read nothing but the tool's README. The tree beside it is grown from that text, here, in your browser. Change a line. Then plant it.

name: wind_bent_coastal_pine

like: pine

siblings: 3

height: [9, 12]

age: old

trunk:

lean: 12

lean_toward: 90

sweep: 0.5

clear: 0.35

crown:

shape: flat

width: 0.8

density: 0.4

gaps: 0.7

branches:

gnarl: 0.4

wind:

from: 270

strength: 0.8

foliage:

kind: needle

leaf_cm: 8

colour: '#2f4a2c'

amount: 1

bark:

texture: pine_plated

Drag a number. Pick a word. Click a line to type.

It will stand on the far shore of the lake, on every page.

Growing…

Wind bent coastal pinePlate I · drag to turn

02

The game speaks JSON

Bandwidth doesn't matter in 2026. So everything the game and its players say to each other is plain JSON, and a new game needs no message format of its own. That means a model can sit down at any Crescent game and play it, one command at a time: look, walk, talk, buy. This is a real session, replayed.

{ "player": { "entityId": 5, "x": 250, "y": 250, "health": 200 },
  "nearby": [
    { "entityId": 2, "entityType": "TaskBoard", "distance": 70.7 },
    { "entityId": 1, "entityType": "Bartender", "distance": 150 },
    { "entityId": 4, "entityType": "Alchemist", "distance": 180.3, "tags": ["npc", "vendor"] },
    { "entityId": 3, "entityType": "GearVendor", "distance": 180.3, "tags": ["npc", "vendor"] } ] }

{ "selected": { "name": "vendor", "entityId": "4", "entityType": "Alchemist" } }

sent interact { "targetId": 4 }

received shop_data { "vendorId": 4, "items": [
    { "itemType": "HealthPotion", "name": "Health Potion", "price": 20, "description": "Restores 50 HP." },
    { "itemType": "AntidotePotion", "name": "Antidote Potion", "price": 30, "description": "Cures poison." },
    … five more ] }

sent move { "x": 100, "y": 150 }

{ "state": { "x": 100, "y": 150, "health": 200 } }

{ "state": { "x": 100, "y": 150, "health": 200 } }

sent buy_item { "vendorId": 4, "itemType": "HealthPotion" }

received gold_update { "gold": 30 }

received inventory_update { "items": [{ "itemId": 2000001, "itemType": "HealthPotion" }] }

{ "inventory": [{ "itemId": 2000001, "itemType": "HealthPotion", "quantity": 1 }] }

A recorded session, replayed.

The tavernat 250, 250

03

So a test can play it

If a model can play the game, it can write the test that plays it. This file is one of about a hundred that run before a change lands. It starts the real game server, joins as a player, walks to the alchemist, buys a potion and checks the gold.

economy-buy.scenariopassed · 2.5 s

# name: economy-buy
# description: Verify buying from vendor deducts gold and adds item
ticks 5;913 ms
log Interact with Alchemist;·
select vendor first type=Alchemist;4 ms
send interact {"targetId": $vendor.id};15 ms
wait shop_data 5000;·
log Shop data received;·
log Move close to vendor before buying;·
send move {"x": $vendor.x, "y": $vendor.y};7 ms
ticks 3;571 ms
log Buy a health potion;·
send buy_item {"vendorId": $vendor.id, "itemType": "HealthPotion"};9 ms
wait gold_update 5000;·
assert last.gold == 30;1 ms
log Economy buy verified — gold deducted from 50 to 30;·

14 steps, 1 assertion, against the real server over a real socket.