Technique · engine

Level loading

How a game stores its levels compactly and expands them into the screen, the collision map, and the objects as play reaches them.

stubAlso: level format, level data, area parser, room loading, level decompression, map loading, level builderUpdated 2026-10-23

Cartridge space is scarce, so levels are stored as compact descriptions and expanded while the game runs. A scrolling game expands each column or row as it nears the screen; a game of rooms builds a room when the player enters it.

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Mentioned in

Games

Every claim about this mechanic, by game (3)
Super Mario Bros.: The Lost Levels 1986The area parser and its object builders (AreaParserTaskHandler through GetBlockBufferAddr) are Super Mario Bros.'s, with most changes in the metatile numbers they write, which shift with the renumbered metatiles (bridges, flagpole, coins, bricks, cannons, stairs, blocks, water pipe). Beyond those: the object jump table gains entries, the wind on and off commands among them, so three offsets into it change; ScrollLockObject_Warp picks the warp zone's destination by world, level and area; the third ledge style uses metatiles $8A-$8C and draws no stem, where Super Mario Bros.'s mushroom ledge uses $19-$1B with a stem (and RenderUnderPart drops its stem checks); the vertical pipes place a piranha plant through a shared SetupPiranhaPlant, with no exception for world 1-1; Jumpspring places nothing when no enemy slot is free. IncrementColumnPos, AlterAreaAttributes, KillEnemies and the object position helpers are byte for byte the same.Code
LoadAreaPointer, FindAreaPointer and GetAreaDataAddrs are Super Mario Bros.'s, with the area data address tables made tables of words (indexed with an ASL) where Super Mario Bros. keeps separate low and high byte tables; the tables themselves hold The Lost Levels' worlds, and AreaDataOfsLoopback its 12 loop points. Of the level data, only the 9-byte pipe intro area (L_GroundArea10) is byte for byte Super Mario Bros.'s.Code
Mega Man 2 1988The last 16 screens of Metal Man's map, $1C to $2B (1,024 bytes), are byte for byte the last 16 of Mega Man's Cut Man and Wily stage 1 map: Cut Man's screens $0C to $0F and Wily stage 1's $10 to $1B. Metal Man's screens $18 to $1B repeat four of them, Wily stage 1's $18 to $1B.Code