game-jam

SKILL.md

Game Jam

Turn a theme and a fixed deadline into a finished, submitted game. This is a planning and
scope-control playbook, not engine code: the win condition is something submitted and
playable, not the game you imagined.

When to use

Use when entering a timed jam (Ludum Dare, GMTK Jam, Global Game Jam, a weekend jam),
scoping a 48-hour build, or deciding what to cut to hit a deadline.

Use when the user asks "what can I actually build in a weekend" or "how do I submit to
this jam".

When not to use: building the core loop in engine code (use the engine skill —
godot-2d-movement, phaser-core, etc. — or a genre skill like platformer); throwaway
experiments with no deadline (use prototype-fast); shipping a commercial release (use
steam-publish / itch-publish).

Core workflow

Read the rules before the theme drops. Confirm the jam's length, theme reveal
time, submission deadline (with timezone), whether teams/pre-made assets/engines are
allowed, and whether ratings require you to rate other entries. Missing one of these
disqualifies an otherwise-finished game.

Prep the boring parts in advance (allowed by most jams): empty project that builds
and exports, input + a title/end screen stub, an export pipeline you've run once, and a
font/SFX source you're licensed to use. Day-one time is too precious to spend here.

Theme → one sentence. Brainstorm 10 ideas in 15 minutes, then commit to one
expressible as: "You [verb] to [goal] while [constraint]." If you can't say it in one
sentence, it's too big.

Scope to the clock, not the idea. Use the budget table below. Pick one core
mechanic and one "hook". Everything else is a stretch goal.

Build the vertical slice first. Get a 30-second playable loop (start → play → lose/win
→ restart) running early. A complete tiny loop beats a half-built big one.

Reserve the last ~20% of the clock for shipping, not features. Export, test the build
on a clean path, capture screenshots, write the page. Builds always break at hour 47.

Submit early, update if time remains. Upload a working build well before the
deadline; most jam pages let you swap the file until it closes. A submitted mediocre game
scores; an unsubmitted great one does not.

Patterns

1. Scope budget by jam length (plan backwards from the deadline)

              | 48-hour jam            | 72-hour jam           | 1-week jam
--------------|------------------------|-----------------------|------------------------
Core mechanic | 1, proven by hour 6    | 1-2                   | 2-3 interacting
Levels/content| 1 hand-made or gen'd   | 3-5                   | 8-12 + progression
Art           | placeholder/1 palette  | cohesive 1-artist set | themed set + UI
Audio         | 3-5 SFX + 1 loop       | SFX + 1-2 tracks      | adaptive music
SHIP BUFFER   | last 8-10 h            | last 12-16 h          | last full day

2. The 48-hour timeline (concrete blocks)

H0-2    Ideate -> lock ONE-sentence concept -> name the core mechanic + win/lose.
H2-8    Core loop in code with primitives (boxes/circles). Make it playable, no art.
H8-12   Sleep. (Tired code is tomorrow's bug list.)
H12-24  Content: 1 level/encounter, tune difficulty, add the "hook" feature.
H24-30  Sleep + playtest with one other person; cut anything not landing.
H30-38  Art + audio pass. Juice: screenshake, hit-stop, tween, particles, SFX.
H38-44  Bug-fix freeze: no new features. Fix only crashes + soft-locks.
H44-48  EXPORT, test the build clean, screenshots, write page, SUBMIT (by ~H46).

3. Feature triage — decide fast, decide out loud

For every feature ask, in order:
  1. Does the core loop work WITHOUT it?   -> if yes, it's a stretch goal, not MVP.
  2. Can a player tell it's missing?       -> if no, cut it.
  3. Is it < 30 min of work?               -> if no, defer past the ship buffer.
Default answer under deadline pressure is CUT. You can always add in a post-jam version.

4. Pre-submission build check (run on a clean copy, not your dev folder)

[ ] Build runs from an extracted zip on a path with NO engine/IDE installed.
[ ] Controls are shown on-screen or on the page (jurors won't read your mind).
[ ] No dev console errors; no soft-lock; restart works.
[ ] Web build (if any) is set to the platform's playable-in-browser mode.
[ ] Page has: 1-line pitch, controls, screenshots, credits + asset licenses.
[ ] File uploaded and the submission is actually attached to the JAM, not just the page.

Pitfalls

Scope creep is the #1 jam killer. If the core loop isn't playable by the first third
of the clock, cut features now, not later.

No ship buffer. Exporting, zipping, and writing the page reliably takes 1-3 hours and
always surfaces a build bug. Treat the deadline as ~2 hours earlier than it is.

Submitting to the page but not the jam. On itch.io a jam entry is a separate
submission linked from the jam page — uploading the game alone does not enter it.

Untested export. "Works in the editor" is not "works in the build." Test the exported
artifact on a clean path; missing assets and wrong working directories are classic.

Unlicensed assets. Music/fonts/sprites pulled from the web can violate jam rules and
break later distribution. Use assets you're licensed for and list them in the credits.

Polishing before the loop is fun. Juice multiplies fun; it can't create it. Get the
loop right with placeholders first.

References

For the throwaway-vs-keep prototyping mindset and greyboxing technique, read the
prototype-fast skill.

For the actual upload mechanics (project page, channels, butler push), read
itch-publish.

Related skills

prototype-fast — validate a mechanic quickly before committing jam hours to it.

itch-publish — create the page and upload the build (most jams are hosted on itch.io).

Engine cores (phaser-core, love2d-core, godot-gdscript, …) and genre skills
(platformer, roguelike, …) — build the actual loop the jam scopes around.