Codex builds a multiplayer Counter Strike prototype
Stepan Parunashvili reports Codex building a playable multiplayer FPS through seven staged requests, with user-supplied errors and a persistence correction.
instantdb.com
Original prompt
Shared by the source author. See source notes for context.
I want you to create a browser-based version of counter strike, using three js.
Reach people exploring AI agents
See placements →Evidence at a glance
Sourced account- Source author
- Stepan Parunashvili
- Original account
- Read the source ↗
- Published
- 26 Nov 2025
- Source link checked
- 15 Oct 2026
- Reported result
- The author links Codex’s playable multiplayer FPS prototype and reports eventual completion after feedback on imports, multiplayer behavior and a map query.
- Human involvement
- The author supplies roughly seven sequential goals and feeds errors back to the agents. The comparison required engineering intervention on the Claude branch.
A linked account supports attribution. It does not mean we independently reproduced its result.
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How the agent did it
- Build a local Three.js FPS with enemies, shooting and respawning.
- Add gun presentation, character shapes, sounds and animations.
- Use Instant presence and topics for multiplayer movement and shots.
Stepan Parunashvili compared three coding agents by asking each to build a simple browser version of Counter Strike. The published account links separate playable outputs for Codex, Claude and Gemini. This case follows the Codex branch, using its default medium reasoning setting with the 5.1 codex-max model.
The developer divided the work into successive goals. First came a Three.js scene with first-person controls, enemies, shooting and respawning. Later requests added character shapes, a visible gun and sound. Once the local game worked, the agent introduced multiplayer movement through Instant presence, shot events through topics and persistent map selection through the database.
Codex initially called a function without importing it and then fixed the error. Multiplayer movement and shooting needed further feedback, and the multi-room step required another round over a query error. The author says the agents eventually built real multiplayer games without code written by hand, but also describes people pasting errors back into the sessions. This was an incremental supervised build. It demonstrates an implemented prototype and correction process, not an unattended replacement for engineering review or a production game.
Prompt
Original prompt
Source: Blog · Stepan Parunashvili
Frequently asked questions
Was the game built with one prompt?
No. The agents received roughly seven consecutive prompts covering frontend mechanics and multiplayer features.
What did Instant provide?
Presence shared player positions, topics carried shots, and the database stored map definitions.
Did the user need to inspect errors?
Yes. The author describes pasting errors back and a further query-error correction for Codex.
More details
Remaining steps
- Add persistent maps, correct a query error and expose room selection.
About this account
Codex inspects the TypeScript library, writes game and multiplayer code, and repairs errors during a staged build.
Firsthand account opened and read. Original page embedded post metadata states date 2025-11-26 and author Stepan Parunashvili. Outcomes are author-reported and were not independently reproduced. Playable deployment links were read in the source, not independently playtested. Original prompt box contains a short excerpt of the author's published instructions.
Credit: Stepan Parunashvili
Source published 26 Nov 2025
Source checked 15 Oct 2026
Tools and topics
Three.js · Instant presence · Instant topics · Instant database
Games · Codex CLI
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.