You've stomped hundreds of them. Now be one.
A Koopa Paratroopa escapes World 1-1 and finds itself in a familiar nightmare: endless pipes, one-hit deaths, and the cruel pull of gravity. Flap to survive. How far can you go?
This isn't a demake or a ROM hack—it's a brand new NES game, handcrafted in 6502 assembly and playable on real hardware.
- Your Koopa has personality. Die and watch it retreat into its shell, peek out nervously, then waddle off-screen in shame.
- Beat your high score? Fireworks. You earned them.
- Battery-backed saves. Your best score is waiting for you next time.
- Sounds like the real deal. Crisp flap sounds, coin chimes, and a melancholy game over tune that wouldn't feel out of place in a first-party Nintendo game.
- Poke around the title screen. Not all Koopas are green...
| Button | Action |
|---|---|
| A / B | Flap |
| START | Play |
| SELECT | ????? |
- Real NES/Famicom (via flashcart)
- Any NES emulator (Mesen, FCEUX, RetroArch, etc.)
One ROM. No compromises. Pure 8-bit.
Grab the ROM from the Releases section—it's free!
If you enjoy the game, consider supporting the project on itch.io where donations are welcome.
Requires the cc65 toolchain.
# Install cc65
sudo apt-get install cc65 # Debian/Ubuntu
brew install cc65 # macOS
# Build the ROM
make
# Build and run in emulator
make runOutput: build/flappy.nes
| Mapper | NROM-256 |
| PRG ROM | 32 KB |
| CHR ROM | 8 KB |
| SRAM | Battery-backed |
See CLAUDE.md for the full technical breakdown—sprite layouts, memory maps, sound engine details, and more.
Built by a human and an AI, pair-programming late into the night. Claude Code (Anthropic's AI coding agent) wrote the 6502 assembly and documentation. The human brought the vision, direction, and the patience to fix the cursed bugs we created together.
See ACKNOWLEDGMENTS.md for special thanks.
Code: MIT License - See LICENSE
Art/Characters: The Koopa Paratroopa, pipes, and other visual elements are Nintendo's intellectual property. This is a fan project made for fun and education, not for profit.