Starter kit for a 2D platformer

What you get

The result

One playable level in a desktop browser: the player runs and jumps across platforms, collects coins, avoids an enemy, and reaches a flag. A title screen, a win screen, sound effects, and a static build you can upload.

7 files

Ready for your agent

• AGENTS.md: the plan, with a check after every step
• first-prompt.txt, install.txt, .mcp.json
• CREDITS.md, CLAUDE.md, kit.json

As a .zip or one by one

13 parts

Every part is free or has a free tier

• Code: MIT, Apache-2.0
• Art and sound: CC0, OFL-1.1
• Agent tools: MIT, Apache-2.0

3 of 3 asset sources allow commercial use with no credit needed. Plus 2 optional parts, off by default.

10 / 10

Checks met in the last test build

• Build 2, Oct 12, 2026
• 27 things in the brief reported, 1 serious
• Findings went back into recipe v0.3

What happened when an agent built from it

Left to you, because no check can do it: Listen to the four sounds once: a check can count play calls, not judge how they sound. Upload the build: it needs your account on the host.

Code

Art and sound

For your agent

Ship

Licenses of the assets

License terms as the sources state them, read on the dates shown. The kit's CREDITS.md starts with these rows and the brief tells the agent to add one for every file it brings in. This is a record, not legal advice.

The plan your agent follows

The agent works one step at a time and does not start a step until the previous one meets its "Done when" lines. The full instructions, with code, are in AGENTS.md.

1. Scaffold · done when:
   • The dev server shows an empty scene at 1280x720 that scales with the window, and the console has no errors or warnings.
   • npx tsc passes.
   • npm run build passes and dist/index.html loads its script from ./assets/.
   • The kit files listed under "Before you start" are still there.
2. Assets · done when:
   • A temporary test scene draws one tile, one character frame and one enemy frame, and plays one sound after a key press.
   • [...document.fonts].map(f => f.family + ':' + f.status) lists the font as loaded, and a screenshot shows text set in it.
3. Level · done when:
   • Screenshots with the camera at the left end and at the right end show ground, platforms and a background.
   • The same two screenshots taken with WebGL (not the Canvas renderer) show no thin vertical lines in the background.
   • A normal visit to the built game has no window.__game; with ?test it has one.
4. Player · done when:
   • A scripted test holds Right until x has grown by 300 px (fail after 5 s), then presses jump: y rises and returns to the ground.
   • A tap of the jump key (give it a hold time in the script, for example 50 ms) peaks lower than a held press, and a zero-length press still jumps.
   • A screenshot with physics debug drawing on shows the body outline on the character, not around the whole frame.
5. Gameplay · done when:
   • Each rule has its own check, and a check may place the player through the hook: a coin overlap raises the counter and the HUD shows it; falling onto a coin does not allow a jump in mid-air; side contact lowers hearts by one and does not repeat for about a second; landing on the enemy removes it; a fall restarts the level with coins and hearts reset; the last heart does the same; a key held across a restart still moves the player; touching the goal sets state to won.
   • A debug screenshot shows every coin's and enemy's body on its art.
   • A screenshot shows the HUD count readable over the sky and over the clouds.
6. Sound and screens · done when:
   • Starting from the title screen, a run reaches the win screen.
   • After the first key press game.sound.locked is false, and the four counters in window.__game.sounds rise during a run.
7. Verify and ship · done when:
   • The playthrough log shows jumps, coins, hits, deaths, wins, the sound counters, the final state, and zero console errors and warnings.
   • Every line under Definition of done is true.

Known traps

What test builds and the official docs showed going wrong with these parts. Each one is in the brief, so the agent reads it before it gets there.

• Phaser 4 is not Phaser 3. The classes Point, Mesh and BitmapMask are gone, and FX and masks became filters. AgentGid: Phaser
• Do not start the project with npm create @phaserjs/game@latest: it only works at an interactive terminal, and its template pins older versions than this kit. checked by running it, Oct 12, 2026
• Kenney's atlases use Starling-style XML: load them with this.load.atlasXML(key, png, xml), then refer to frames by name. Phaser skill: loading-assets
• A font whose path has a space, in the file name or in a folder, fails to load with a warning only, and the game silently uses a system font. document.fonts.check() still answers true, so look at a screenshot. Phaser source and test build
• Two Phaser skills disagree about fonts. The text skill says Phaser cannot load web fonts; the loading-assets skill documents this.load.font, and that loader exists in 4.2.1. Use it. Phaser skills, checked Oct 12, 2026
• Browsers block sound until the first key press or click. Phaser unlocks audio by itself after that, so start the game from a title screen and do not add your own workaround. Phaser skill: audio-and-sound
• A game with no sound at all has a clean console. Count the play calls, or nothing checks the audio. test build
• itch.io accepts at most 1,000 files in a ZIP, and this pack alone has 1,353 entries: ship the atlases and sounds you use, not the whole pack. itch.io docs
• The physics skill's first example calls setCollideWorldBounds(true). With world bounds equal to the level, that turns the bottom of every pit into a floor. test build
• The engine's own bundle contains strings such as SNES_USB (its gamepad tables). A search of dist/ for console brand names finds them: they are not yours to remove. test build

Checks on this kit

• Note Phaser is at 4.2.1 on npm. Models often write Phaser 3 code from memory, so the brief points the agent at the skills shipped inside the package. Source
• Note The chosen pack has 1,353 entries and itch.io allows 1,000 files per upload. The brief tells the agent to copy only the atlases and sounds it uses. Source

What happened when an agent built from it

The recipe was given to a fresh coding agent in a clean sandbox, twice. The agent got only the kit files. It had to build the project and write down everything in the brief that was wrong, missing or unclear.

Result of the last build. A playable level, 22 files and 1.7 MB, finished by a scripted playthrough in 26 seconds. Its findings went back into the recipe, which is now at v0.3. That version has not been built again as a whole.

Art and sounds: Kenney, New Platformer Pack (CC0). Font: Lilita One (OFL-1.1). Screenshots of the project the test agent built.

Checked again on Oct 19, 2026. AgentGid checks every recipe each week, without a model: 4 pinned packages all still exist on their registries, 1 of them has a newer release than the tested pin; 24 links in the brief: all open. npm lines are checked pin by pin, not installed.

Not checked by anyone yet

• How it sounds: nobody listened
• The upload to itch.io
• Browsers other than Chromium
• A machine with a GPU
• The pixel and 1-bit styles, and plain JavaScript

The kit files

Put them in an empty project folder, open your coding agent there and paste the first prompt (Claude Code first asks you to approve the MCP servers in .mcp.json). These are the files for Claude Code with the default answers; the kit builder writes them for Cursor, Codex, Copilot or another agent, and for other choices. Full guide: how to use a kit.

Download all (.zip)

Read AGENTS.md from top to bottom before you do anything else. The kit files it lists are already in this folder.

Then do step 1 of the plan and stop. Report back with:
1. the commands you ran,
2. what each "Done when" check showed (a screenshot or the output),
3. anything in AGENTS.md that turned out to be wrong, missing or out of date.

Do not start step 2 until I reply.

Read AGENTS.md from top to bottom before you do anything else. The kit files it lists are already in this folder.

Then work through the plan in order. After each step, run its "Done when" checks yourself and write one line in PROGRESS.md: the step, what you checked, and the result.
You may install the packages and download the files that AGENTS.md lists without asking. Stop and ask me only for what its "Before you start" section says needs a person.
When a check fails, fix the cause and run it again. If it still fails after two real fixes, stop and tell me what you tried.
Keep a list in PROGRESS.md of anything in AGENTS.md that turned out to be wrong, missing or out of date.
When every line of the Definition of done is true, stop and show me how to run it.

npm install --save-exact phaser@4.2.1
npm install -D --save-exact vite@8.3.4 typescript@7.0.2 @playwright/test@1.64.0

Other versions of this kit

Other versions were not test-built as a whole: the kit says which parts differ from the tested one.

Ask for this kit from your agent

Agents connected to the AgentGid MCP server get the same kit without this page: list_recipes(), then plan_project({"recipe": "2d-platformer", "answers": {"agent": "cursor"}, "files": true}). Every brief also tells the agent to ask AgentGid before it adds a part that is not listed.

Recipe 2d-platformer v0.3. Data snapshot Oct 12, 2026: versions, licenses and prices change, so check the linked pages before you ship.

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