# Asset Loader

## Current state

PNG loading is implemented in `game/src/assets.rs`. `Image::from_png(path)` decodes via the
`png` crate (any color type, expanded to 8-bit RGBA) and quantizes on load to the
framebuffer's RGB565 format with `pbio::rgb565`; alpha ≥ 128 counts as opaque. The result
is an `Image { width, height, pixels: Vec<u16>, opaque: Vec<bool> }`. Artists work in
truecolor; there is no palette an asset could be "in the wrong order" for. `game.rs` uses it
directly: `Image::from_png("assets/tilesets/overworld.png")`.

`Image` also provides `to_tileset() -> Vec<Tile>`, which splits the image into 8×8 tiles
row-major. A `Tile` is 64 RGB565 pixels plus a `u64` opacity bitmask. Every tile is
emitted; tile ID is the flat row-major index into the Vec, so tiles are never skipped or
reordered. `overworld.png` is the unmodified Mini-Medieval `Overworld.png` sheet (24
columns), so Tiled tile ids line up with the Vec index.

History: the first iteration used 8-bit indexed TGAs on a palette framebuffer (RGB332,
`pbio` master branch). The colormap-ordering fragility and the index-0-is-transparent
convention are gone with the switch to `pbio`'s `truecolor16` branch.

`AssetStore` (a named registry) is **not yet implemented**. Assets are currently loaded
inline in `Game::start()`.

## Goal

Add an `AssetStore` so that game code can ask for an asset by name rather than loading
files directly at the call site.

## Design notes

- `Image` struct: `width: u32`, `height: u32`, `pixels: Vec<u16>`, `opaque: Vec<bool>` — done.
- A simple `AssetStore` could be a `HashMap<&'static str, Image>` loaded at startup.
- No streaming needed — the whole game is small enough to load everything upfront in `start()`.
- Transparency is the tile's mask bit, checked by `blit_tile()` in `pixelhelper.rs`. Any
  color — black included — can be an opaque pixel.
- Pixel assets are stored as flat `Vec<u16>` of RGB565 values, row-major, width × height.
- Future: consider embedding assets with `include_bytes!` to produce a single binary.

## Open questions

- Should `AssetStore` hold pre-split tilesets too, or just raw `Image` values?