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I built a full game in about a week. Here's my actual workflow.

180 upvotes61 commentsFeb 24, 2026

The Game

Castle Battle: Castle vs castle combat, trebuchets, magic spells, and trying to blow up the other guy before he gets you. Real-time combat with timing, combos, and a little strategy built in.

Stack

Phaser JS, Codex, Claude, and a tool I'm building called AutoSprite for all the graphics and animations.

TLDR

  1. Exhaustive PRD + screenshot mockup

  2. Codex 5.3 → “Implement this end to end."

  3. Claude Opus 4.6 → bug fixes, make game fun, iterate, mcp for graphics

  4. AutoSprite for graphics, Tonejs for sound

The week broke down like this

Day 1: Planning mode. Used AI to write a stupidly detailed PRD. Every screen, every spell, every enemy behavior, gameplay flow, typical game flow example. How things interact.

Then mocked up one screenshot of what I wanted it to look like, you can do this with any image gen or pen and paper or excalidraw.

The PRD is the most important part, you should spend a lot of time on your PRD and try to cover every aspect of your game.

Day 2: Threw the PRD and mockup screenshot at Codex 5.3. Prompt was basically "implement this end to end." It one shot a working skeleton. Physics, UI, game loop, all there and functional but ugly.

Day 3-6: Switched to Claude Opus 4.6. This was the "make it actually fun" phase. Bug fixes, game tweaks, new spells, flashy effects, particle effects, using AutoSprite MCP to create the actual assets and animations. Using tonejs for sounds

Day 7: Polish. Camera zoom, flashy effects, more particle effects, extra juice.

All castles, spells, abilities, animation spritesheets came from AutoSprite. SFX and music via Tonejs, coded directly.

Happy to get into the weeds on prompts, why I picked this stack, or anything else!

Open live experience