Building BLADEFALL: every prompt and every bug
A 3D top-down arena fighter built in one Claude Code session — the prompts used, the bugs we hit (including a game that restarted itself), and how each one was fixed.
BLADEFALL is a 3D top-down arena fighter — three levels, four enemy types, a three-phase boss, procedural sound, and zero downloaded assets. It was built in a single Claude Code session. This is the short, honest build log: the exact prompts, and the problems we hit along the way.
▶ Play the game — WASD to move, F or click to attack, Space to dodge.
The prompts
Five prompts (lightly edited for grammar):
1. The whole game in one prompt:
"Make a really good 3D fighting game, top-down. Use whatever tech you want — Three.js or anything else — with proper sound, loading screens, levels, and so on. Make sure the game is playable, the enemies are smart, and it's fun, with proper feedback effects."
That produced the entire first version: Three.js renderer, procedural humanoid characters, WebAudio-synthesized sound and music (no audio files), enemy AI with an attack-token system so enemies take turns instead of mobbing, hit-stop, screen shake, damage numbers, loading screen, three themed arenas, and a boss.
2. Bug report from playtesting:
"There are some issues: the WASD controls are janky (I tried it), and the game sometimes restarts on its own."
3. Ergonomics:
"The keys are too far from each other — pressing K while playing is hard. Fix it."
4. The port:
"Now turn this into a Next.js project and keep the game at the page /claude-fable-game."
5. This post:
"See how we write blogs in ../aireels — we need a similar blog for this site at /blog."
The problems we faced
Enemy attacks crashed the game. The enemy state machine called this.executeAttack() — a method that was never written. Every enemy windup threw a TypeError. Caught immediately because Claude ran the game in a real browser after writing it and read the console, instead of assuming the code worked.
Wave 2 never spawned. A classic closure bug: setTimeout(() => startWave(G.wave + 1)) read G.wave after it had been set to a guard value of -99. Captured the next wave number in a local constant before scheduling.
The game restarted itself (part 1). After clicking "Enter the Arena", the button silently kept keyboard focus — so pressing Space to dodge re-clicked the button and restarted the run. Buttons now blur themselves on click.
The game restarted itself (part 2). Even after that fix, hidden menu buttons were still reachable with Tab — and Tab sits directly above W. Tab then Space activated an invisible "Restart Level" button. Fix: Tab is swallowed, buttons are removed from the tab order, and every button is state-guarded so "Retry" physically cannot fire unless you're on the death screen.
The ghost player. Mid-session, the game appeared to be playing itself — level 3 reached with zero input. Claude spent a while debugging stacking contexts before realizing the human was playing the game in the same browser window the tests were running in. Lesson: agents and humans sharing one browser is chaos.
Janky WASD. Two causes: movement acceleration used a slow exponential lerp (~a third of a second to reach full speed), and attacks locked you in place for their full recovery. Fixes: ~3× snappier acceleration, faster stops, and "move-cancel" — holding a direction cancels the back half of an attack's recovery. Also: keys no longer stick when the window loses focus.
K was too far away. Light attack moved to F, heavy to E — both reachable without leaving WASD. Mouse-only also works (left click light, right click heavy).
React StrictMode ran the game twice. In the Next.js port, dev-mode StrictMode mounts every component twice — which means two renderers, two audio engines, two input handlers. The game module now returns a proper destroy() that cancels the animation frame, clears every timeout, removes every listener, and closes the AudioContext. Verified: exactly one canvas after mount.
The stack
- Next.js 15 (App Router) — game at
/claude-fable-game, this blog at/blogs - Three.js — characters, arenas, and effects are all procedural geometry
- WebAudio — every sound effect and the music are synthesized at runtime; the repo contains no asset files at all
Every fix above was verified by actually playing the game in a browser (via Playwright) — clicking Start, dispatching real key events, and asserting on game state — not by re-reading the code and hoping.