Under Tetris Holding, LLC v. Xio Interactive, Inc. (863 F. Supp. 2d 394), pure rules (falling geometry, line clears) are unprotectable ideas, but exact board dimensions, ghost piece silhouettes, block color hierarchies, and display fonts constitute protectable audiovisual expression.
✓ Unprotectable (Free to Use)
- Falling block clearing mechanic
- Randomized piece generation
- Score tracking & speed ramp
- Grid-based movement rules
✗ Proprietary Trade Dress
- Original 7-tetromino color layout
- Exact 10x20 well aspect ratio
- Korobeiniki 8-bit theme melody
- Identical ghost piece outline
- Remove proprietary visual trade dress and distinct piece silhouettes
- Include conspicuous disclaimers of non-affiliation with original rightsholders
- Shift from proprietary sound design/branding to generic public domain audiovisual assets