There’s traditionally a milestone during production called “vertical slice”, where the developer would present a segment of the game that’s meant to represent the final product. They’re not necessarily considered best practice, since a developer might have to pantomime that the game’s in a finished state when they still have a lot of work to do. Tim Rogers describes it akin to making a cake one slice at a time.

Mark Cerny, a developer for a lot of Sega and Sony titles, always suggests an experimental pre-production phase and a structured production. The former is meant to figure out the requirements for the latter and clarify the nature of the product.