Limitations of the Game Boy with GBDK

Elsie's Out of Potions » Devlog
57 days ago by jeffzzq
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I have written a longer form post about some of the limitation of the Game Boy with accompanying examples. I had some issues writing longer content for Work Life so I won't really bother with that again.

You can check out the post here (there should not be a paywall): https://jeffzzq.medium.com/some-limitations-of-the-game-boy-67d94a8afb8a

And take a look at the code here: https://github.com/jgensler8/gbdk_bad_examples

What I cover:

  • animation with background tiles
  • sprite limits
  • window flickering
  • rom overwriting

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bbbbbr23 days ago

Cool to read the writeup and some of the things you encountered. Here's a couple tips that might be useful for using the GBDK toolchain:

> never render empty sprites and use up a vital sprite slot

Yes, png2asset operating in "metasprite" mode (the default, i.e. without "-map") will accomplish that. It treats tile regions with no pixels set as empty space and skips over them, so that when the metasprite frame is loaded into the OAM no sprite slots will be used for empty tiles. It is typically used with *_metasprite_*() functions which will update all the needed sprite entries at once.

> loading a whole new set of data + rewriting the bg map every animation frame

For multiple background images (or sprites) that share a common tileset the -source_tileset option for png2asset might be useful. It allows generating tilemaps that don't require reloading the tile if the shared tile data is already in place (or only reloading the tiledata that is unique and not shared).

There is also the gb\hblank_copy demo which demonstrates a way to load vram data faster for background animations that don't have tearing. It can be for tilemaps or tile data.

Hope these help if you work on a GBDK project again.

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jeffzzq22 days ago

Thank you for taking a look! I would like to revisit the Gameboy / GBA at some point, probably the next time a Jam rolls around. I'll take a look at the metasprite code again. I did take a look at the hblank example so maybe I can verify it helps with the example repo I put in my post.

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