IOCCC 2025: 22 Winners, One 366-Byte Program That Boots Linux and Doom
The 29th International Obfuscated C Code Contest returned its 2025 winners: 22 entries selected from what judges called near-historic submission volumes, including a GameBoy emulator whose source code is shaped like a GameBoy and a 366-byte C program that runs Linux, Doom, and implements a one-instruction computer architecture.
Three authors — Yusuke Endoh, Nick Craig-Wood, and Don Yang — each took three prizes, a hat-trick that has happened only rarely in IOCCC history.
Craig-Wood, creator of rclone, wrote ncw1: a Game Boy emulator where the source code itself is laid out in the shape of a Game Boy hardware unit.
The entry "cable" fits a Subleq OISC virtual machine capable of running Linux and Doom into 366 bytes of C. The thread called it a favorite; one developer noted it implements a One Instruction Set Computer architecture.
IOCCC Returns With Its Highest-Quality Field in Years
The 29th IOCCC winners page went live and immediately pulled 373 points on HN — one of the top scores of the week. The contest had been on hiatus from 2020 through 2024; this is only its second running since resuming. Judges described the volume and quality of 2025 submissions as "at near-historic heights." In the thread, C veterans arrived with strong opinions about specific entries.
22 Entries, Three Hat-Trick Authors
The contest awarded 22 winning entries. Three authors claimed three prizes each: Yusuke Endoh (endoh1, endoh2, endoh3), Nick Craig-Wood (ncw1, ncw2, ncw3), and Don Yang (yang1, yang2, yang3). A first-time winning author from Taiwan (jingp49) extended the contest's geographic reach.
Selected highlights:
| Entry | Award | What it does |
|---|---|---|
| cable | Best imaginary emulator | 366-byte Subleq OISC VM that runs Linux and Doom |
| ncw1 | Best real emulator | Game Boy emulator; source code shaped like a Game Boy |
| endoh3 | Most resilient | Patch/diff quine |
| uellenberg | Ping pong prize | Quine pong |
| tompng | Most soothing | Ocean sound generator |
| yang2 | Most magical word | Zoltraak encoding (Frieren reference) |
| jhshrvdp | Most likely to teleport | Quasi-rogue-like game |
| cesmoak | Retro space award | Black hole punchcard Fortran |
The Thread: Veterans Pick Their Favorites
The entry drawing the loudest admiration was ncw1. The author, Nick Craig-Wood, is the creator of rclone — a widely-used open-source cloud storage tool:
"The GameBoy emulator's code also looks like the GameBoy. Slow clap this is insane, definitely my favorite entry." — a commenter active since 2019
But another commenter made a strong case for cable, the most structurally ambitious entry in the set:
"My favorite is the 366-byte C program emulator that can run Linux and Doom. The VM implements an OISC — a One Instruction Set Computer." — a commenter with an OpenRISC Linux emulator in their bio
One commenter had a personal connection to the winning set:
"OMG, my game boy game of life implementation is included in one of the winning entries!" — a commenter active since 2020
A backend developer shared the IOCCC's most durable use case — the job interview:
"Back in 2000 I was being interviewed for my first internship, to join a team of C programmers. They showed me one of the winner entries of the prior years, asked me to review the code and left the room… 'I'm sorry I wasted your time. I just can't understand it.' They burst into laughs and asked me to start the joining process." — a backend developer active since 2020
The contest's survival in the LLM era generated its own subthread. One commenter questioned whether the competition still has meaning given that LLMs can now obfuscate code on demand; others pushed back that the creative constraint — source shaped like a Game Boy, a 366-byte VM that boots Doom — is exactly what LLMs cannot yet generate with intentionality and wit. The contest explicitly permits LLM use in its guidelines, which at least one commenter found noteworthy.
What Survives the Automation Question
The IOCCC's value was never pure obfuscation difficulty. It was always the combination: technically valid C that compiles, does something remarkable, and rewards close reading with a joke or a structural surprise you didn't see coming. The cable entry's 366-byte Linux-booting VM is a specific engineering achievement. The ncw1 source code shaped like a Game Boy is a visual gag that requires planning the layout before writing a single line of logic. These aren't tasks where "make it obfuscated" is a sufficient prompt. The contest resumed from a four-year gap with its best field in memory. That answers the automation question more directly than any argument does.
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