📀 PS22004NamcoVERY HARD

Katamari Damacy rebuild deck

VERY HARD

You will get a good prototype. The product is what comes after.

The attachment maths is a lovely, self-contained problem that an agent solves well, and geometry merging is the one part that needs real engineering attention or the frame rate dies at object 500. The reason it is only a KINDA is tone: Katamari is a mood, and the mechanic without the music and the King is just a growing ball.

Difficulty: VERY HARD · 4 of 5
First playable: A weekend
The original: 12 team-years
Released: 2004 · PS2
Genre: Action

The one-shot build prompt

Build a rolling-accretion game in the Katamari mould. three.js plus a physics engine, third-person.

Requirements:
- A ball that rolls with dual-stick style controls: both sticks forward to move, opposed to turn in place. Support keyboard equivalents. Momentum matters; the ball should feel heavy and slightly hard to steer.
- The core system is attachment: any object whose bounding radius is below a threshold relative to the ball's current radius sticks on contact. On attachment, freeze the object's physics body, reparent its mesh to the ball at the contact point with its contact orientation, and grow the ball radius by the cube root of the added volume. Getting the growth curve right is the whole game — it must feel like doubling in size takes exactly as long at every scale.
- Performance: attached objects must be merged into batched geometry, not kept as thousands of separate meshes. Re-merge on a budget, a few objects per frame, so growth never stutters. This is the hard engineering problem here.
- The ball's silhouette gets lumpy as objects attach, and that lumpiness must affect the roll — apply a small torque wobble scaled to how uneven the attachments are.
- World built in scale tiers: a tabletop, then a room, then a street, then a city block, each becoming reachable as the ball grows. Objects at the wrong scale are immovable obstacles that shove you.
- Camera pulls back logarithmically with ball radius, always framing what you can currently pick up.
- A timer, a target size, and a results screen listing the largest and most absurd items collected.

Definition of done: I roll over a cat, then a car, then a building, and the moment each becomes possible feels earned.

Before you start🧰 The toolkit — models, MCP servers, art and 3D

What you lose

The soundtrack, which is genuinely half the game
Thousands of individually modelled everyday objects at every scale
The tone — a prompt does not give you the King of All Cosmos
Level design across five orders of magnitude of scale

What to steal

Compounding growth with a logarithmic camera

Growth that compounds, paired with a camera that zooms logarithmically, makes minute forty feel exactly like minute one at a thousand times the scale — the same trick idle games and RPG level curves live on. Get the object size distribution log-uniform or the pacing dies in the middle and you will blame the growth rule.

ScopeAn evening— build just this, not the game

Build a rolling-accretion toy in two dimensions as a single self-contained HTML file. Canvas 2D, no physics engine, no build step.

- A disc you steer with real momentum, on a plane scattered with circles whose radii span four orders of magnitude, from a pin to a tower block.
- The attachment rule is relative, never absolute: a circle sticks if its radius is below a fixed fraction of yours, around 0.4. Anything bigger blocks you and shoves you aside.
- On attachment, add its area to yours and take the new radius from the square root, then stick its outline onto your rim so the silhouette gets visibly lumpy. In three dimensions this is the cube root of volume; the principle is that growth compounds.
- Camera zoom is logarithmic in radius, so the disc occupies the same share of the screen forever.
- Distribute object sizes log-uniformly. Plot time-to-double on screen as you play.

Definition of done: time to double my radius stays within twenty per cent of constant from the first minute to the last.

Make it different

Not a clone — Katamari Damacy 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 Flatland

Katamari Damacy, but 2D instead of 3D, set in the Wild West. Rendered in PS1 low-poly with texture warping.

Themethe Wild West

Angle2D instead of 3D

LookPS1 low-poly with texture warping

Build a browser game called "Blackpowder Flatland".

The pitch in one line: a action in the spirit of Katamari Damacy, but 2D instead of 3D, set in the Wild West.

WHAT THIS IS
Take the SHAPE of Katamari Damacy — 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
2D instead of 3D. Canvas 2D and sprites. The mechanics survive the dimension drop; the asset budget falls by an order of magnitude.
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
PS1 low-poly with texture warping. Vertex-snap positions to a low-resolution grid in the vertex shader, use affine texture mapping so textures swim, dither to 15-bit colour, and fog the draw distance.

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.

Prior art — read before you build

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.

Did you build it?

0Share on X

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 12 team-years to the counter on the homepage.

Then try these

Or roll something nobody has built yet →

Questions

How hard is Katamari Damacy to rebuild with an AI agent?

Yes — every game is buildable at some scope. The question is how hard, and Katamari Damacy is VERY HARD (4 of 5). You will get a good prototype. The product is what comes after. The attachment maths is one evening and the geometry batching another; what no prompt gives you is a thousand hand-modelled objects spanning five scale tiers, and without them the ball grows through an empty world. Reckon on a weekend to something you can actually play — not to something that matches the 12 team-years Namco spent.

What makes Katamari Damacy hard to rebuild?

The attachment maths is one evening and the geometry batching another; what no prompt gives you is a thousand hand-modelled objects spanning five scale tiers, and without them the ball grows through an empty world. That is why it sits at VERY HARD rather than a tier either side of it. If you want the idea without the project, the transferable part is compounding growth with a logarithmic camera — an evening of work.

How long does it take to build a Katamari Damacy clone?

Wrong question, and it is worth saying why. Nobody rebuilds Katamari Damacy — the original took Namco on the order of 12 team-years, released in 2004 on PS2. What you can do is reach something playable and genuinely yours in about a weekend, 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 Katamari Damacy?

The soundtrack, which is genuinely half the game. Thousands of individually modelled everyday objects at every scale. The tone — a prompt does not give you the King of All Cosmos. 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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