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A developer reports that Claude (Opus 5.5) built a complete browser-based ‘Stickman Arcade’ — nine free games plus an animator, roughly 24,500 lines of dependency-free JavaScript — in a single day from an open-ended prompt. The headliner, rhythm brawler BEATDOWN, was playable in under an hour. The claims come from the developer’s own account and have not been independently verified.

A developer who asked an AI model to build ‘its own stickman game’ with no further specification says the result was BEATDOWN, a rhythm-based stick-figure brawler — and that by the end of the same day the project had grown into a Stickman Arcade of nine free games plus an animation tool, all running in a browser, as detailed in our full coverage. The developer, who published the account on the blog Thorsten Meyer AI, states the entire arcade was coded by Claude (Opus 5.5), Anthropic’s model, with the human writing no code at all (see the original account).

According to the account, the brief was deliberately loose: no clone, no tutorial project, just the model’s own take on the stickman genre. The AI returned BEATDOWN, a brawler in which every attack is judged against a soundtrack generated live in the browser. On-beat hits deal 1.5x damage; landing four consecutive on-beat hits triggers a bonus attack with a shockwave; and enemies telegraph on one beat and strike on the next, allowing a timed guard to convert into a counter. The developer reports rhythm is a bonus rather than a requirement — players can clear waves off-beat, but tighter timing adds musical layers and raises a ‘Groove’ rank from MUTE to FEVER.

The roster is described as twelve original fighters built around musical archetypes — Drummer, Conductor, DJ, Bassist, Punk, Soprano, MC, Jazz Cat, Shredder, Virtuoso, Beatboxer and Producer — each with a passive ability, two specials, a cooldown skill and an ultimate called the DROP, for sixty abilities in total. The arcade offers nine art styles (CHALK, RISO, LASER, SHEET, ZINE, PIXEL, BRUSH, BLUEPRINT and NOIR) that the developer says change how everything is drawn, not just colours, and seven venues with distinct rules — a wall-less Rooftop, a tilting Cruise Ship deck, a dark-between-beats Strobe Rave — plus modes including TOUR, BOSS RUSH, BLITZ, DAILY MIX and two-player VERSUS.

The remaining eight games reportedly run on the same engine: Stickman Dismount, Pose-Off, Beat Runner, Noir Heist, Band Defense, Stickman Boxing, Head Soccer and Beat Skate. A tenth card is a Stickman Animator for posing figures by dragging joints and exporting GIFs or sprite sheets. The developer states there are no image or audio files — everything is generated by code — in roughly 24,500 lines of plain JavaScript with zero dependencies, including a custom GIF encoder, with no data collection and progress stored locally.

What This Shows About AI Coding Scope

The account matters because it illustrates the current scope of AI-assisted development on a single, open-ended task. Rather than a code snippet or a demo, the reported output is a multi-game product with shared architecture — the developer says the AI wrote a shared game kit and an engine guide, then built each game on top of it. If accurate, the scale (roughly 24,500 lines of dependency-free JavaScript, an embedded GIF encoder, live music generation) points to AI models handling sustained, multi-session software architecture rather than one-shot generation.

It also highlights the shifting role of the human: the developer describes their contribution as steering — answering the model’s questions, sending screenshots of games they liked, and repeatedly asking for more. That division of labour, where the model writes all code and the person curates direction, is the working pattern many non-programmers and studios are now testing. For readers, the story is less about one arcade than about what a single vague prompt and a day of iteration can now produce.

From Vague Prompt to Working Game

The project began, according to the account, with a deliberate experiment: give the model a genre everyone knows — stickman games — and let it decide everything else. The developer reports BEATDOWN was playable in under an hour and live on their site in under two. After the first game, the human kept requesting more, and the AI restructured the work into a shared engine before adding the eight additional games and the animator, ending with the arcade’s ten animated cards presented in whichever of the nine art styles the user selects. The games are free, run in any browser, and support touch controls on phones.

“I gave an AI model a deliberately loose brief: make your own stickman game. No clone, no tutorial project, just its own take on a genre everyone knows.”

— Thorsten Meyer AI, developer account

Claims Not Independently Verified

All core claims come from a single first-person account. The 24,500-line codebase size, the one-day build time, the zero-dependency architecture and the ‘no data collection’ statement have not been independently audited. The developer also acknowledges the post itself was created with the assistance of AI, which readers may weigh when evaluating it. It is not clear from the account how much iteration and prompt-steering time was involved beyond the described day, how the games perform across devices, or whether the model’s stated version and behaviour are reproducible for others. Bugs, balance issues and long-term maintenance of AI-generated code are not addressed.

Where the Arcade Goes From Here

The arcade is live and free in browsers, so readers can evaluate the claims directly by playing it. The developer’s pattern — one vague prompt, then repeated requests for more — suggests possible additions or refinements may follow, though none are announced. More broadly, the account adds a data point to an ongoing debate about how far AI coding tools can carry entire products and what verification, review and maintenance practices should apply to largely machine-written software.

Key Questions

What is BEATDOWN?

According to the developer, it is a stick-figure rhythm brawler in which every attack is timed against a soundtrack generated live in the browser. On-beat hits deal 1.5x damage, and playing well adds musical layers and raises a Groove rank from MUTE to FEVER.

Who wrote the code?

The developer states that Claude (Opus 5.5) wrote all of it in one day — roughly 24,500 lines of plain JavaScript — while the human directed the project, answered questions and sent reference screenshots. This claim is from the developer’s own account.

How many games are in the Stickman Arcade?

The arcade is described as containing nine games — BEATDOWN plus Stickman Dismount, Pose-Off, Beat Runner, Noir Heist, Band Defense, Stickman Boxing, Head Soccer and Beat Skate — along with a tenth card, the Stickman Animator.

Do the games work on phones, and do they collect data?

The developer says the games run in any browser with touch controls on phones, collect nothing, and store progress locally in the user’s own browser. The data-collection claim has not been independently verified.

Are there image or audio files in the games?

According to the account, no. Every fighter, venue, sound effect and music layer is generated by code while the game runs, with zero external dependencies — including a GIF encoder written for the animator.

Source: Thorsten Meyer AI