A from-scratch Pong clone for the Atari 2600 (NTSC), written entirely in 6502 assembly against the real TIA/RIOT hardware — no framebuffer, no high-level engine, just a hand-counted display kernel building the image line by line, the way it actually worked in 1977.
Classic 2-player Pong, playable in the Stella emulator or on real Atari 2600 hardware (the ROM is exactly 4096 bytes — fits a 2732 EPROM or a flash cart like the Harmony/UnoCart).
- Two paddles, one joystick each, first to 5 points wins.
- Ball physics with some texture, not just a bouncing square:
- Random serve direction and angle every point (3 angle profiles × 4 quadrants), so no two serves play the same.
- Speed starts slow at serve, then climbs in small, even steps as a rally goes on — fast enough to feel earned, capped so it never catches up to the paddle's own speed.
- Paddle "English": hit the ball while your paddle is moving and you add spin to the rebound angle, same idea as the real game.
- Real Atari-style state machine: the game sits frozen at power-up until you press GAME RESET; win a match and the screen freezes with the final score up and the background flashing until RESET starts a new one — RESET restarts instantly from any state, including mid-rally, matching how the real console switch behaves.
- 3-stage paddle-size difficulty, cycled with GAME SELECT.
- Big, classic-scale scoreboard above the court, a dashed center net, and a hit/score beep on the 2600's own sound chip.
| Input | Action |
|---|---|
| Joystick (left/right port) | Move that side's paddle up/down |
| GAME RESET | Start a new game / restart instantly at any time |
| GAME SELECT | Cycle paddle size (full → 3/4 → 2/3 → full) |
Windows:
.\build.ps1 runNeeds dasm.exe in tools\ and Stella installed — see
docs/DEVELOPMENT.md for the one-time setup
(both are a few minutes, no Visual Studio or SDK required).
macOS/Linux: brew install dasm stella, then the reference Makefile
in docs/DEVELOPMENT.md.
Real hardware: build/game.bin is a plain 4K binary — write it to a
2732 EPROM (or a 2764 with the image duplicated twice) on a donor/generic
cartridge board, or just load it on a Harmony/UnoCart flash cart.
No engine, no assembler macros beyond register names — every frame is 262 scanlines, budgeted to the cycle, written by hand:
- 6502 assembly, assembled with DASM.
- 128 bytes of RAM total (the entire working memory of the machine).
- Paddles, ball and the center net are real TIA hardware objects (players/missile/ball), positioned with the classic divide-by-15 routine; ball↔paddle collision uses the TIA's own hardware collision latches rather than software bounding-box checks.
- The digit font for the scoreboard is a hand-derived 7-segment design, scaled up via NUSIZ width-doubling and row-repeat to read at a classic-Pong scale instead of a thin sliver.
- Serve randomness comes from a software 8-bit Galois LFSR (the 2600 has no hardware RNG) — advanced every frame regardless of game state, so the exact value at any given serve depends on unpredictable human reaction time.
The full build process, hardware reference notes, and the running log of
engineering decisions (and the debugging sessions behind a few of them)
live in docs/DEVELOPMENT.md and in src/main.asm's
own header — this project was built iteratively, in public-style commits,
with Claude Code doing the assembly work
end to end.
Feature-complete as a 2-player game. Not yet done: an AI opponent, and
sound beyond the hit/score beeps. See
docs/DEVELOPMENT.md for the detailed
checklist.
MIT — use it, fork it, learn from it.