🃏 Classic1935Parker BrothersHARDMonopoly rebuild deck
HARD
The rules are a weekend of bookkeeping and every one of them is mechanical, but the game is four people arguing over a trade — so you are not building a board, you are building multiplayer state, and an AI that will not trade is an AI nobody plays twice.
You will get the loop working. Then the real work starts.
Split this honestly. The board, the movement and the rent tables are a mechanical weekend and a prompt gets you most of it working. Then there are two separate projects hiding behind it: trading AI, and real multiplayer. Trading is the one worth doing — it is a small valuation model plus a negotiation loop, and it is what makes the thing playable solo. Multiplayer is a server, an auth story and a month, and you should decide before you start whether you actually want that.
- Difficulty
- HARD · 3 of 5
- First playable
- A project
- The original
- 2 team-years
- Released
- 1935 · Classic
- Genre
- Strategy
Build a Monopoly-style property trading game, hot-seat for 2-4 players plus AI opponents. Vanilla JS or React, no backend — all state in one reducer. Requirements: - Board of 40 spaces, eight colour groups, four railroads, two utilities, tax, chance and community chest, jail and go-to-jail. Rename everything: your own street names and a title that is not the trademarked one. - All state in a single serialisable object mutated only through named actions (ROLL, BUY, BUILD, MORTGAGE, OFFER_TRADE, ACCEPT_TRADE, PAY, BANKRUPT). Build it this way from the first line — this is what lets you add online play later without a rewrite. - The rules that are actually fiddly, and where hand-rolled versions go wrong: doubles roll again, three doubles is jail, rent doubles on an unimproved monopoly, houses must be built evenly across a group, and the house supply is finite at 32 — the building shortage is a real strategy and most clones silently ignore it. - Bankruptcy resolves properly: mortgaged properties transfer with the debt, and to a player rather than the bank when a player caused it. - AI opponents that trade. Each holds a valuation per property — base price, plus how much completing that group is worth to it, minus what it costs the other side — and will propose and accept unequal deals when the group completion is worth it. It must be able to lose a trade on cash and win it on position. - Trade UI: drag properties and cash both ways, live 'they will probably accept' indicator, counter-offers. - Game log of every transaction, and a cash-over-time chart at the end. Definition of done: an AI proposes a trade I did not expect, I take it, and I lose because of it.
- Trading that feels like trading — a bot that values property correctly still cannot be talked into a bad deal, and being talked into bad deals is the game
- Four people at a table, which is where the shouting, the alliances and the entire point live
- Real-time multiplayer without a server: the moment it is not hot-seat you need authoritative state, reconnects and a way to stop someone editing their own cash
- The Hasbro name and board art — the rules are yours to implement, the trademark and the box are not
An opponent that negotiates from a private valuation, not a fair-value table
Most trading bots compute an objective price and refuse anything below it, which makes them vending machines — you learn their number once and the negotiation is over forever. Give each bot its own valuation shaped by what it is trying to complete and what it thinks you want, and the same property is worth different amounts to different players at different moments. That single change is what turns a rules engine into a game with people in it.
ScopeA weekend— build just this, not the game
Build a trade-negotiation sandbox as a single self-contained HTML file. DOM, no dependencies, no board required. - Six abstract assets belonging to three sets. Three AI agents plus you, each holding a random subset and some cash. - Every agent values an asset privately: a base value, plus a completion bonus if it finishes one of their sets, plus a denial value if holding it blocks someone else. Agents do not see each other's valuations. - Agents propose trades to each other and to you, and accept anything that beats their current position by a margin they set. They may include cash to balance a deal. - Show each agent's private valuation table on a debug toggle, plus every offer made and refused, so a rejected deal is explainable after the fact. - Run 100 rounds with no human and chart who accumulated what. Definition of done: with the debug panel off, an agent talks me into a trade that looked fair and was not, and the valuation table afterwards shows exactly why.
Not a clone — Monopoly re-themed and cut down to something you can finish. The angle is the important reel: it is what turns a project into a weekend. 24,360 ways to land.
Blackpowder Play By Mail
Monopoly, but asynchronous multiplayer — no live server, set in the Wild West. Rendered in silhouette against one light.
Build a browser game called "Blackpowder Play By Mail". The pitch in one line: a strategy in the spirit of Monopoly, but asynchronous multiplayer — no live server, set in the Wild West. WHAT THIS IS Take the SHAPE of Monopoly — its core loop, and whatever makes that loop good — and rebuild it as your own game in a different world at a smaller scope. Use your own names, art and audio, which you want anyway: a reskin of somebody else's game is less interesting than a new one that works the same way. THE ANGLE — this is the important constraint, honour it above everything else Asynchronous multiplayer — no live server. Players take turns hours apart against stored state. You get real multiplayer with none of the real-time netcode. This is what makes the project finishable. If a decision would push the scope back towards the original's, take the smaller option every time. THE THEME The Wild West. Distance, dust and long reloads. A single main street the whole design hangs off. The theme is not a coat of paint. Let it change what the mechanics mean — a reload, a health pack and a locked door should all be things that make sense in this world and nowhere else. LOOK Silhouette against one light. Everything renders pure black against a lit background, with depth from four parallax layers of increasing blur, grain and a heavy vignette. REQUIREMENTS - Runs in a browser with no build step. Canvas 2D unless the angle genuinely requires 3D, in which case three.js. - Fixed-timestep update loop with interpolated rendering, so it behaves the same at 60Hz and 144Hz. - Every tuning constant in one CONFIG object at the top, exposed as live sliders in a debug panel. You will find the feel by dragging those, not by prompting. - All content — levels, entities, balance numbers — in JSON or plain data files, never inline in the logic. - Audio generated with the Web Audio API rather than asset files. - Respect prefers-reduced-motion: keep the fades, drop the shake and the parallax. BUILD ORDER 1. The core loop with placeholder rectangles, at the reduced scope the angle demands. No theme, no art, no audio. Make it fun as rectangles first. 2. The angle's consequences. Cutting to bots, or to turn-based, or to one level changes the design rather than just shrinking it — find out how and rewrite step 1. 3. The theme, as content and data. 4. The look, applied last as a rendering layer over a game that already works. Start by writing a one-page plan: the core loop, what the angle removes and what that frees you to do properly, and what you are deliberately leaving out. Wait for me to approve it before writing code.
- boardgame.io — turn phases, player state and hot-seat/online in one model
- colyseus — authoritative rooms if you take it online
Half the time one of these already does what you wanted, and the other half it saves you a week of solving a problem someone documented in 1997.
One count per game. No account — it is tied to a salted hash of your IP, which is not stored in a form anyone can reverse. Every build adds 2 team-years to the counter on the homepage.
Then try these
Questions
How hard is Monopoly to rebuild with an AI agent?
Yes — every game is buildable at some scope. The question is how hard, and Monopoly is HARD (3 of 5). You will get the loop working. Then the real work starts. The rules are a weekend of bookkeeping and every one of them is mechanical, but the game is four people arguing over a trade — so you are not building a board, you are building multiplayer state, and an AI that will not trade is an AI nobody plays twice. Reckon on a project to something you can actually play — not to something that matches the 2 team-years Parker Brothers spent.
What makes Monopoly hard to rebuild?
The rules are a weekend of bookkeeping and every one of them is mechanical, but the game is four people arguing over a trade — so you are not building a board, you are building multiplayer state, and an AI that will not trade is an AI nobody plays twice. That is why it sits at HARD rather than a tier either side of it. If you want the idea without the project, the transferable part is an opponent that negotiates from a private valuation, not a fair-value table — a weekend of work.
How long does it take to build a Monopoly clone?
Wrong question, and it is worth saying why. Nobody rebuilds Monopoly — the original took Parker Brothers on the order of 2 team-years, released in 1935 on Classic. What you can do is reach something playable and genuinely yours in about a project, and then keep going for as long as it stays interesting. Any figure that claims otherwise is measuring a prototype and calling it a game.
What do I lose by building my own Monopoly?
Trading that feels like trading — a bot that values property correctly still cannot be talked into a bad deal, and being talked into bad deals is the game. Four people at a table, which is where the shouting, the alliances and the entire point live. Real-time multiplayer without a server: the moment it is not hot-seat you need authoritative state, reconnects and a way to stop someone editing their own cash. Those are the parts a prompt will not hand you.
Which AI coding agent should I use to build it?
Any of Claude Code, Codex or Cursor will handle this prompt. Paste it as your first message, let the agent scaffold the project, then iterate on feel — the second, third and tenth prompts are where a game actually gets good. Work in an empty folder or a fresh git branch so you can throw it away cheaply.
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