Why a Vertical Slice Beats a Full Prototype

Clients often ask for a broad prototype touching every planned feature. In practice, that spreads a limited budget thin across ten half-working systems instead of one system that's actually fun to play.

A vertical slice gives stakeholders one level and one core loop built close to final quality. It provides something concrete to test instead of a list of planned features.

It also de-risks the rest of the project. Problems in the core loop show up immediately in a vertical slice, while a shallow prototype can hide them until much later, when they're far more expensive to fix.