Levelsio says Claude Code helped port Battlefield 1942 to the browser

• Battlefield 1942’s demo now runs in a browser, as levelsio’s first video demonstrates.
• Claude Code handled a machine-code-to-C-to-WebAssembly conversion, including graphics and networking rewrites, according to his technical account.
• The project consumed roughly one million output tokens on a $100/month Claude subscription, according to his usage post.
• Multiplayer capacity went from 16 to 64 slots between his first server update and his follow-up.

He says he revived a six-month-old failed attempt with “Opus 5.5” and the prompt “can you try port the BF1942 demo in this folder to web”. The build ran on a MacBook Pro before deployment to Ubuntu, according to his reply about the setup.

Levelsio says he started with compiled machine code and worked through six stages:

1. Disassembly: Identify approximately 57,000 x86 functions in the executable.
2. x86 → C: Translate machine instructions into C functions. His example turns mov eax, [esi+0x110] into eax = READ32(esi + 0x110).
3. C output: Generate approximately 100,000 lines of C.
4. C → WebAssembly: Compile that output with Emscripten.
5. Windows/Direct3D → WebGL 2/OpenGL: Rewrite approximately 300 platform-specific functions for the browser.
6. Multiplayer networking: Build a custom network stack connecting the browser client to a multiplayer server through WebSockets.

The playable project’s page identifies the graphics work more specifically as DirectX 8 reimplemented on WebGL 2. Rebuilding those Windows-facing interfaces is the impressive bit.

Emscripten’s graphics documentation describes an OpenGL subset that maps directly to WebGL; its networking documentation explains that browsers cannot open TCP sockets directly.

The server hit its 16-player ceiling after launch. Levelsio then announced 64 slots: 16 → 64, +48 slots.

Across his old-game ports, he also claimed faster loading than on his RTX 5090 gaming PC. The posts provide no timed loading comparison, frame-rate measurements or latency results.

Levelsio says the work ran through his $100/month Claude subscription. Expanding from output alone to every category in his usage ledger changes the accounting:

• Tokens counted, in millions: 1.0 → 291.2, approximately +290.2 million tokens when input and cache operations are included. Most of that volume consists of repeated reads of cached context.
• Estimated API cost, in dollars: 19.99 → 102.50, approximately +82.51 dollars when input and cache operations are included.

These comparisons count the same run at different scopes; the dollar figures estimate API billing.

Levelsio describes this as harder than his Quake and DOOM ports: those benefited from existing open-source work, while Battlefield 1942 had no open-source engine to build on, according to his account.

The playable scope is the free demo, as he emphasized in a reply. He also calls the game “abandonware”.

EA’s November 2012 announcement offered a free PC copy through Origin, subject to conditions. That announcement contains no permission to publish a modified browser build.

The browser project describes itself as non-commercial, unofficial and unaffiliated with EA or DICE.

Levelsio’s Quake III and DOOM projects already offer browser multiplayer. He describes the goal as “open tab, instant multiplayer”.

His other creator invitation is more outdoorsy: in a separate conversation, he offered to travel and film walks with people doing interesting work.