Megadev levels

Start with the game's map scale, camera, collision convention and resource owners. Megadev does not provide SGDK's MAP/resource pipeline. Tiled authoring data needs an explicit importer and a game-owned runtime format; the Lab's lv_* functions are application code, not SDK APIs.

Define an import contract

Use Tiled importing to choose supported orientations, tile sizes, transforms, layers and object classes. The supplied importer supports a small finite orthogonal profile with a shared 16×16 atlas; unsupported features fail explicitly. Expand that contract when the game needs more instead of silently approximating its artwork or geometry.

Preserve editable source maps and images. Prepare on the host, then verify source/output hashes during container builds. Do not make a normal build regenerate demonstration layouts over a designer's changes. Reject stale prepared data, invalid exits and colors outside the assigned palette before compiling a disc.

Keep world data separate from presentation

Use collision, cameras and exits for collision cells, foot boxes, stable spawn identities and named connections. A visible tile is not necessarily solid. Camera clipping, failed sprite admission and foreground occlusion must never change collision or interaction. Validate destination spawns and keep arrival outside exit triggers.

Reuse the game's simulation clock. Small bounded walking steps can use grid checks; fast objects need megadev-collision's swept queries. Define interaction and arrival behavior from the user's game rather than importing the Lab's controls or progression.

Bound scrolling and residency

Read Megadev rendering and residency before changing plane size, scroll registers or resource ownership. Stage incoming rows/columns with the matching camera and sprites; publish them together in VBlank. Late submission must keep the old complete view, not expose partially refreshed tiles. Match the VDP plane dimensions to the cache's wrap arithmetic explicitly.