I Gave Claude, Codex, and Gemini the Same App to Build. Then I Made Them Blind-Judge Each Other.

I had a dumb little experiment I wanted to try. And, as dumb little experiments sometimes do, it got way more interesting than I expected. I gave three coding agents the exact same task: Claude (Opus 5) Codex (GPT 5.6 Sol) Gemini (Gemini 3.7 Flash) All set to medium. The assignment was to build an Arkanoid-style browser game from the same specification. Nothing particularly groundbreaking. Arkanoid is small enough that an agent can build a complete version in one session, but complicated enough to expose differences in physics, architecture, UI, audio, controls, testing, and general decision-making. The important part was that they all started with the same instructions. Then I let them work. No fixing their mistakes afterward. No "you forgot this feature." No giving one of them another pass because something looked weird. Whatever they decided was finished was their submission. But building the games wasn't actually the most interesting part. Afterward, I gave all three games back to all three agents, anonymized as CL , CO , and GE . They did not know who created which game. They were just told that they were judging 3 contest submissions by the creators' initials. And that's where things got, well, fun. The three games You can actually play all three versions: Gemini: https://arkanoid-gemini.pinkpixel.dev Codex: https://arkanoid-codex.pinkpixel.dev Claude: https://arkanoid-claude.pinkpixel.dev All three produced working games, but they approached the assignment very differently. That difference started showing up before I even looked closely at the code. First difference: how long they worked I didn't originally intend runtime to be part of the experiment, so unfortunately I wasn't sitting there with a stopwatch. These are rough observations, not benchmark numbers. But the difference was large enough to be impossible to miss. Gemini: roughly 5 minutes Codex: roughly 10 minutes Claude: more than 20 minutes Gemini absolutely flew through it. That's not especially sh