Tile Map

The map consists of tiles to create the world.

GBA graphics are made out of tiles with a size of 8px by 8px. We call those tiles subTiles. Four of those subTiles are combined together to form a bigger 16px by 16px tile (usually called metaTile). We call these tiles.

Each map can be up to 64 * 64 tiles big. The map consists of two layers of tiles gMapTop and gMapBottom. To access the map array the tilePos index can be used which goes from 0 to 64 * 64 = 4096. Each value in the MapLayer.mapData is a tileIndex which defined which tile of the tileSet should be used. The tileSet contains tiles from 0 to 2048. Special tileIndex from 0x4000 to 0x4096 can be used to denote special tiles.

A tile is created from four subTiles. The subTiles for each tile in the tileSet are stored in MapLayer.subTiles. This is loaded for the current area from gAreaTileSets_*. The subTiles can also be flipped or the palette changed. This is stored in bits 0xa to 0xf, see https://www.coranac.com/tonc/text/regbg.htm#sec-map.

Each tile in the tileSet also has a tileType defined. This is stored in MapLayer.tileTypes and loaded from gAreaTileSetTypes_*. The inverse dictionary from tileType to tileIndex is stored in MapLayer.tileIndices.

The map also stores the collision for each tile in the tileMap layer in MapLayer.collisionData. By default this is filled from gMapTileTypeToCollisionData based on the tileType of the tiles. But it can also be loaded from gRoomCollisionMap_*. In MapLayer.actTiles some additional type for each tile is stored which is filled from gMapTileTypeToActTile based on the tileType of the tiles.