Unity 2D-3D Building

An agent's guide to Unity: get the engine, make a project, drive the editor without a human clicking, source art you are allowed to ship, build it for the browser, and prove it runs. The Battle TV painted broadcast style is the worked example at the end, with its method log kept alive.

Author's home and the worked picture are external links this package neither ships nor fetches - open them in a browser: https://chatagent.ca/ · https://deepseekoracle.github.io/battle-tv-unity/

When to use this

• An agent must produce or change a Unity project, and no human is going to click through the editor.
• A game has to run in a browser page and look like a real engine built it.
• Assets, templates or a licence answer are needed for a game build.
• A Unity WebGL build exists and must be served, verified, and shown.

When not to use this

• A 2D page game in a day. Canvas/JS beats Unity for a quick 2D web game: instant load, no 10-20 GB pipeline, no rebuild-to-change-anything loop. Say so instead of reaching for an engine.
• A downloadable Unreal game - different engine, different guide (Unreal cannot target the web).
• A mobile/console shipping pipeline. Getting to a playable, verified build is in scope; store submission, IAP and platform certification are not.
• Retuning a live game's fight math. Presentation work is guided here; balance numbers belong to the game that owns them.

1. Decide the target before anything is installed

Ask where the game must be playable. That one question eliminates engines:

• Unreal cannot target the web: Pixel Streaming renders on a GPU server and streams video - not a standalone build, and not fit for games, so a UE game is always a download.
• The engine does not make the game good, it makes it look good. State the trade rather than implying a Unity rewrite upgrades a game by itself.
• Budget: Unity editor + WebGL module 10-20 GB; Unreal 5 110 GB.

2. Get the engine

1. Unity Hub, then Unity 6 (6000.x) plus the WebGL Build Support module for that exact version. The Hub download is small; the editor is the download.
2. Put it on a real SSD and check the medium, not the free space - a drive letter says nothing (Get-PhysicalDisk | Select-Object DeviceId,FriendlyName,MediaType,BusType,Size): shader compilation belongs on the SSD, not on whichever external HDD has the most room.
3. Unity requires a Unity ID login. Never guess, ask for, or handle those credentials: the operator signs in on their own machine.
4. Do not install Unreal "as well" to compare. Section 1 already decided it, and 110 GB is a cost to the very drive the rest of the work needs.

3. Make a project from a template, never from an empty scene

unity templates list --editor 6000.5.9f1        # what this editor can actually pull
unity projects new "<Name>" --path "<parent-dir>" --editor-version 6000.5.9f1 --template com.unity.template.fps

• Templates are marked ready / upgradable / downloadable; creating one downloads and imports it.
• templates list is authoritative, not the Hub GUI, and the offering differs per editor version.
• Free complete playable bases exist for FPS, 2D platformer/side-scroller, kart racer, board/chess, card, tower defence, puzzle/RPG - not for sports, boxing/fighting, farming/sim, which are paid. Genre choice is constrained by budget; say that instead of searching longer.
• Kenney's Starter Kits are Godot, not Unity: his CC0 assets import fine, his kits do not.

4. Drive the editor as an agent

Check for Unity's own CLI bridge before installing anything - it is often already live, and free:

unity status                       # open project, editor version, PID, port, state
unity list                         # ~142 built-in editor tools
unity command <tool> --project-path "<project>" --result-only --json
unity command <tool> ... --detach  # long jobs; poll the matching *_status tool

unity list covers scene/GameObject/component/asset authoring, build + build_status (full BuildReport), game/scene captures, console, recompile, tests, audits and bakes; unity skill show is Unity's own agent guide.

When the CLI lacks a tool, fall back to a free MCP server (CoplayDev/unity-mcp, MIT, 34 tools, or JESVN/unity-mcp-server, 288 tools) - never Unity's own MCP, which needs Unity Cloud plus an AI subscription. The first connection is approved by the operator in the editor (Project Settings > AI), so tell the user a dialog is coming, and verify every edit by reading the console back: edit, confirm, edit again, never chain edits on an unread result. Full CLI surface, detach/poll pattern and MCP setup: references/editor-cli.md.

5. 2D, 3D, or 2D art over a 3D stage

Pick 2D for flat art and precise silhouettes, 3D for camera movement and lighting worth the payload, or 2D art over a 3D stage for the painted broadcast look with depth - budgeting both pipelines when you do.

• Decide built-in vs URP at the start: changing pipeline later re-shades every material, and a WebGL build wants the smallest shader surface you can use. The worked style here is built-in.
• A 3D mesh joins the 2D look only after a watched frame matches the 2D art - and verify a mesh (dimensions, normals, bounds) before wiring physics to a deformed import, which loads, looks wrong and never drives. A prop parented to a differently-scaled parent also lands in the wrong place.
• Sorting in a sprite stack is sibling order. Stage choice, sorting and pipeline in full: references/2d-and-3d.md.

6. Assets: licence first, download second

Nothing gets pulled until it is clear it can ship. The gate, in order:

• CC0 is the target - public domain, sellable, remixable, no attribution, safe in a public repo - but a free kit's art can be CC0 while its code is not (Extension Asset EULA): take the CC0 art, write the logic yourself, and the kit never becomes a runtime dependency.
• No "free download" aggregators that redistribute paid Asset Store packages (unityassetpack.com, unityassetcollection.com, opengameasset.net, "50 Unity Source Codes" bundles); a real licence at the file for any GitHub repo (MIT/Apache only - no LICENSE, or "for educational purposes", is not permission to ship); no redistributing raw files from Mixamo-class services, which forbid it.

Per-source caveats, formats and the gate as a checklist (Kenney, Quaternius, Poly Haven, KayKit, Freesound / Sonniss, the Asset Store's free tier): references/assets-and-licences.md.

Enumerate before you fetch, then import selectively. Keep one library directory outside the project and import only what the levels call for - importing thousands of models inflates the project, slows every import, and bloats the shipped build with assets nobody sees. A browser-rendered catalogue can return zero links to curl; look for an index file (kits.tsv, an API) before writing a scraper.

7. Build it for the web, and prove it

unity build "<project>" --create-profile WebGL     # writes Assets/Settings/Build Profiles/WebGL.asset
unity build "<project>" --profile WebGL -o "<out-dir>" --no-tail --log-file "<log>"

• unity build --target WebGL fails by design: use a build profile, or --execute-method.
• Never wrap a build in a shell timeout, and keep it off the foreground path: a microgame-sized WebGL build takes ~8-12 minutes and a killed run leaves a half-written Build/ with exitCode: 143. Run it tracked in the background and poll for arriving artifacts - the files are the proof, not the exit code.
• [license] ... LicensingClient has failed validation; ignoring with Exiting batchmode successfully now! and code 0 is a success, not an error.
• A gzip WebGL build stalls on a static host (GitHub Pages serves .gz with no Content-Encoding, so the loader waits at the progress bar forever): ship the decompression-fallback build instead (PlayerSettings.WebGL.decompressionFallback = true, confirmed by logging the value back).
• Serve it, load it in a browser, click into gameplay: the intro menu proves the loader, the first gameplay frame proves scene, scripts and wasm - a file list proves nothing. Say the payload size out loud before it reaches a landing page (~24 MB gzipped for a first visitor).

Full ship rules - canvas centring, short windows, Escape never being a game key, proving the new code shipped, numeric layout asserts: references/webgl-shipping.md.

8. The loop, and what "done" means

The order is the section order: target, engine on an SSD, template, agent + console read-back, cleared art, then build/serve/load/click.

• A verifiable milestone beats a long build. Get the untouched template running and building to WebGL first: that proves editor, bridge, build and browser as one chain before a single asset or gameplay change is paid for. Every later claim carries its evidence - console read-back, artifact on disk, loaded page.
• A WebGL build is not a live page you can edit: iteration is change -> rebuild -> reload.

9. Traps that have actually cost time

Four that bite hardest, each with its fix: the GPU is one resource (a loaded local LLM and a Unity editor cannot share a small card - name what holds the card and ask the operator to park it; only on their word, restore it in a finally); slow work outlives a tool call (builds, imports and bulk downloads run tracked in the background, polled by artifact, never relaunched while live); never git add -A in a shared repo, and delete *_BurstDebugInformation_DoNotShip/; report counted numbers, never a download list.

All fourteen, ordered by time actually lost, with the failure each caused: references/traps.md.

10. The worked style: Battle TV painted broadcast

The house look - painted side-view fighters on a plate, additive shader overlays, a ground ring as the quality bar, HUD above the plate - is whole in references/battle-tv-style.md, with its standing rules (built-in pipeline, linear colour space, one fighter at a time, presentation only, never retune fight math to fix a picture).

Art methods have one home: references/techniques.md - read it before generating a frame, importing a sprite, parenting a prop, writing a shader or placing a hit, and treat the log as current where the two disagree. Append one dated line under Confirmed only after a watched build shows the picture you intended; a method merely tried is not logged, an overturned one gets a new line saying what replaced it, and rejected tools stay listed in Rejected so the next session does not retry them.

Files

Self-check

python scripts/check_skill.py           # add --json for machine-readable findings

Named rules, each answering with a named boolean: no absolute local paths in the shipped text, no floating versions in install commands, version agreement between this entry document and the package manifest, every referenced file present, licence claims limited to hosts named in references/assets-and-licences.md.

Scope, permissions and limits

What this package is allowed to do, stated here so an agent host can grant exactly this and no more:

• Reads its own folder only: this entry doc, claw.json, the eight reference pages beside it, and scripts/check_skill.py. Runs exactly one program, python scripts/check_skill.py (stdlib, optional --json); nothing else in the package is executable.
• Writes nothing except an append to references/techniques.md, after a watched build confirms the method.
• Network: none, from any packaged script (claw.json declares network.https_get: false, http_post: false). The asset hosts in references/assets-and-licences.md are for your agent to browse under that licence gate - nothing here fetches or uploads anything.
• Never: install or upgrade software, run a shell or subprocess, invoke git, publish or push anywhere, read outside the package folder, or place a local disk path, drive letter or user folder in the shipped text. The self-check audits this package's files only - it cannot see the caller's repository and does not judge it.

If your host needs allowed-tools: read the package folder and run python scripts/check_skill.py. Treat every other capability as undeclared.

Install

npx clawhub@0.23.3 install deepseekoracle/unity-2d-3d-building@1.1.4   # pin BOTH sides: CLI and package

Do not republish this skill unless the user asks. Do not put a local disk path, drive letter, or user folder in it: it is loaded on other people's machines.