build a working computer from scratch, entirely in code, starting from individual logic gates. design the CPU, the memory, an assembler, a tiny operating system, and a game that runs on it. everything has to be real, the game has to run on your gates, not in javascript pretending. visualize the whole thing in 3D so i can play the game, then zoom all the way down through the chips into the gates and watch the signals flow while it runs. treat it like you're proving you could have invented computing yourself. go all out.
Make it yours. Change "a game that runs on it" to the program you want to watch run, and keep "everything has to be real, the game has to run on your gates, not in javascript pretending." The sentence starting "visualize the whole thing in 3D" is what gives the zoom from the desk down to the gates.
A computer built from 277k NAND gates
NAND-16, a computer simulated from 277,248 NAND gates, with a CPU, memory, an assembler, a tiny OS, and a Tetris-style game running on it, on a 3D desk you can zoom through down to single gates. Opus 5.5 built it from one prompt over about 30 hours.
“This isn't a mockup... it's a computer.”
- Claude Opus 5.5
- One-shot
- 30h
- Max plan
How it was made
The creator says it was "done from one prompt, completely autonomously, over ~30 hours in ultracode mode", with 277k logic gates in JavaScript, an OS on top, and games on the OS. He doesn't name the agent.
One Max plan; the creator says he had tokens to spare and didn't hit his limits once.
Claude Opus 5.5
About 30 hours, running on its own in ultracode mode
Source and credit
X · Sep 27, 2026 · 1.8k likes · 274k views · 152 comments
Authorship not stated by the source
Published instructions: Reply on X
Look notesby Reference
A dark, cyan-lit interface around a retro computer on a desk: a title card, the NAND-16 boot screen and a falling-block game on a CRT, then a zoom through the motherboard into glowing logic-gate diagrams.
- Color
- Near-black navy with cyan and teal glow, amber-yellow on active gates, a cream CRT case on a wooden desk, and green-grey chips.
- Type
- A clean sans-serif title ("A computer built from 277,248 NAND gates. Designed by Opus 5.5."), white captions in dark pills at the bottom ("It boots its own operating system", "Slow the clock to 4 Hz", "Fault Lab: break one gate"), blocky pixel text on the CRT, and small monospace readouts.
- Framing
- 16:9. The scene fills the frame with readout panels in the top left, a clock control bar along the bottom, and a minimap in the bottom left; zoomed views show the gates as a flat glowing schematic.
- Structure
- Title card, the boot menu (NANDTRIS, SNAKE, MONITOR, LIFE), NANDTRIS on the CRT, the motherboard with MASK ROM, SRAM, and VIDEO RAM chips, one full adder, the clock slowed to 4 Hz, bullet time with a signal chart, the Fault Lab, and a closing card, "Zoom in yourself.", with the site address.
