# GFX Mental Model

Status: pedagogical
Companion spec: [`../specs/04-gfx-peripheral.md`](../specs/04-gfx-peripheral.md)

PROMETEU treats graphics as an explicit peripheral, not as a modern GPU.

The right mental model is a retro 2D machine with:

- framebuffer;
- tile banks;
- tile layers;
- sprites por ordem de desenho;
- deterministic composition per frame.

## Why This Exists

The goal is not to imitate historical hardware byte for byte. The goal is to capture the family of constraints and visual language of consoles such as SNES, CPS-2, and Neo Geo in a small, portable contract that can run on desktop and DIY hardware.

That produces some important consequences:

- draw order matters more than "effects";
- palettes matter as part of asset design;
- the programmer thinks in terms of rasterization, not shaders;
- visual cost becomes more observable.

## What The GFX Is Not

PROMETEU GFX is not:

- a modern GPU pipeline;
- an RGBA framebuffer with arbitrary alpha;
- a shader system;
- automatic post-processed composition.

Those absences are deliberate. They force a visual language closer to classic consoles and keep the contract executable in modest environments.

## Practical Intuition

- Tile layers exist for world and scenery.
- HUD exists for fixed information and should remain decoupled from the camera.
- Sprites exist for moving entities, and their depth depends on order and priority.
- Palettes exist to vary visual state without duplicating tile art.
- Fade exists as a discrete special effect, not as generic alpha.

## Palette Thinking

A good way to think about PROMETEU is that art and color are not the same thing.

The tile is the shape. The palette is the visual state.

That enables:

- enemy variation;
- biome changes;
- damage, ice, poison, power-up states;
- HUD themes;
- day and night cycles.

## Use Cases

- area transition with `Scene Fade`;
- HUD transition with `HUD Fade`;
- damage flash or teleport flash;
- global palette swap for weather or world state.