https://github.com/bbbbbr/rolly_scrolly_gameboyshowdown_2025
Hastily made little GB Demo for Game Boy Showdown 2025
https://github.com/bbbbbr/rolly_scrolly_gameboyshowdown_2025
Last synced: 12 months ago
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Hastily made little GB Demo for Game Boy Showdown 2025
- Host: GitHub
- URL: https://github.com/bbbbbr/rolly_scrolly_gameboyshowdown_2025
- Owner: bbbbbr
- License: unlicense
- Created: 2025-05-21T02:58:42.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2025-05-21T04:10:24.000Z (about 1 year ago)
- Last Synced: 2025-05-21T05:22:59.474Z (about 1 year ago)
- Language: C
- Size: 321 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
## Rolly Scrolly Demo
Hastily made little GB (And MegaDuck) Demo for Game Boy Showdown 2025 with a Cylinder like effect and some wraparound sprite text.
ROM downloadable on itch.io:
https://bbbbbr.itch.io/rolly-scrolly-demo
### Effect
For the Cylinder:
- Per scanline Y scroll adjustments from a pre-computed table (made in a spreadsheet) that create the cylinder distortion
- There is a matching set of per scanline GB palette adjustments which darken the colors toward the top and bottom of the cylinder
For the bounce:
- There's a per-frame sine wave table that adjusts where the cylinder is located (by setting an initial Y scroll offset which the cylinder code factors in)
For the Text:
- The entire cylinder only uses Background (BG) colors 1-3, and the area outside of it is all scrolled to a single line which only uses BG color 0. This is important for the next part
- For hiding the text that goes "behind" the cylinder the sprites on the left 1/4 and right 1/4 of the screen have their BG priority set so that they only show up over BG color 0 (above and below cylinder area) and are hidden by anything with BG color 1-3 (inside cylinder area)
- Then there is a second sine wave table which is used for the text Y position, this is just indexed based on the sprite X position
### Building
Built with GBDK-2020 4.4.0