Build a vertical slice — prove one polished slice at target quality

The transition from pre-production to full production, and any point you need to prove feasibility or the quality bar (pitching, funding, team alignment).

A prototype proves the game is fun ("should we make this?", PROTO-0001); a vertical slice proves the team can produce it at the intended quality ("can we make it?") [S-proto-vertical-slice]. It de-risks production by forcing every discipline — art, code, audio, design, UX — through one representative piece at shipping fidelity, surfacing the real cost and the real bottlenecks before they're multiplied across the whole game. It also aligns the team on a concrete quality target ("this good, everywhere") far better than a document can, and it's the most persuasive artifact for funding, publishers, and recruits because it is the game in miniature. Choosing a tiny, representative slice is the craft — the temptation to show everything defeats the purpose.

Pick the smallest slice that is representative of the whole game, and build it to final quality across all disciplines. Use it to measure real production cost and extrapolate the full schedule (feeding PROD-0004). Treat it as a quality benchmark and a de-risking exercise, not a demo to endlessly polish. Keep the prototype (fun) and vertical slice (feasibility) distinct — they answer different questions.

Slice-first (prove feasibility and bar before scaling) vs. lighter-weight approaches (prototype then build, common for tiny teams who can't afford a full slice). The value of a slice scales with the project's size and risk; for a solo micro-game it may be unnecessary ceremony.

The production complement to PROTO-0001: prototype = "should we?", slice = "can we?". Feeds scheduling (PROD-0004) and the scope commitment (PROD-0001). Confidence 4.