A vertical slice isn't a demo, a trailer, or some kind of game preview.

It's a working fragment of the project that shows what the game will be like in its finished form.

Simply put:

A vertical slice answers the question

"If we continue making the game in this form, does it make sense?"

Why a vertical slice:

- Testing an idea in practice

A vertical slice shows:

- whether the basic concept works;

- whether the mechanics, visuals, and controls are in harmony;

- whether the project has coherence.

Decision-making point:

It's at the vertical slice stage that decisions are usually made:

- whether the project should be scaled;

- whether a publisher should be involved;

- whether development in its current form should be continued.

Separates reality from speculation:

Before the vertical slice, the project may exist "in the mind."

Afterward, it only exists in reality.

What a vertical slice should contain

A vertical slice is:

- one complete gameplay cycle;

- basic mechanics in working order;

- an example of the final visual style (even if without polish);

- a rough pacing and feel of the game.

Important:

better a little but honest than a lot and a crude one.

What a vertical slice should avoid:

- blanks "for later";

- temporary solutions without a clear understanding of the final look;

- content for the sake of volume;

- attempts to impress with quantity.

A vertical slice is the main test before full implementation.

Typical mistakes:

- Confusing a vertical slice with a demo.

- Making a vertical slice too early, without a foundation.

- Making it too late, when too many resources have already been invested.

- Using it as marketing material instead of an analysis tool.

How a publisher views a vertical slice

For a publisher, a vertical slice is:

- an indicator of team maturity;

- confirmation or refutation of USPs;

- a basis for risk assessment.

- A publisher looks not at "beauty," but at the convergence of elements.

The main point:

A vertical slice is an honest conversation about the project between developers and publishers. It can inspire, or it can shatter illusions. Both options are crucial for the final implementation.

A project without a vertical slice is a hypothesis.

A project with a vertical slice is a subject for discussion.