Greybox

A greybox is an early blueprint for a game level, built entirely from plain shapes like boxes and cylinders with no textures, colors, or detailed design applied.

It's similar to how an architect builds a model of just the walls and room sizes in plain grey concrete before decorating the interior. There's no color or texture, but it lets you check the spatial feel and gameplay flow ahead of time — where players walk, where they jump, how sightlines open up. Game developers use greyboxes to validate a level's fun factor and flow first, then apply the actual art style and theme on top afterward.

Recently, a new approach has emerged where this greybox is handed to an AI model, which then generates multiple finished prototypes in different themes, like cyberpunk or fantasy. Instead of a person decorating everything from scratch, a human sets up just the skeleton, and the model fills in the rest of the visual expansion.

The article states, "After refining this greybox through several iterations, the Playco team had Astra expand it into different themes." Here, the greybox isn't a finished game but an unfinished, textureless skeleton — and it's easy to misread this as the AI creating a perfect game on its own from this stage, but in reality, a human first establishes the spatial structure before the theme is expanded on top of it.

To get a feel for greyboxing yourself, try drawing a room and a corridor using nothing but a few rectangles and circles on paper or in a drawing tool. Then you could ask an image-generation AI something like: keep this simple shape layout, but render it with textures and lighting like a cyberpunk-themed game level. Seeing the result makes it clear why developers set up the skeleton first and apply the theme later.