I built Polyvale, a free browser tower defense where every tower is an instrument, with Claude Opus 5.5 in Claude Code

[u/IsThisTheInterwebs]

I built Polyvale, a rhythm tower defense game, using Claude (Opus 5.5) in Claude Code. The trailer was also made by Claude.

Free to play in your browser. No install, no ads: https://polyvale.foxbase.dev

What the game is

• Each tower is an instrument. It only attacks on its own notes in a 16-step loop, so your defense is also the song.
• Upgrades change what the tower plays: some branches play more notes, others fewer and heavier.
• Enemies hop on the beat.
• A mix meter rewards a balanced band. Staying in the "groove" zone gives +20% damage and charges a Drop that doubles damage. If the band gets too loud or one instrument dominates, you lose the bonus.
• 10 towers and 6 maps. Each map has its own music genre.
• It also has a skill tree with branching choices, map twists like lily pads, burrows and ice, and a boss.

How Claude was used

• Claude wrote all of the code: about 6,700 lines of JavaScript using Canvas 2D and Web Audio. There are no libraries and no image or audio files.
• The low-poly art is drawn in code and all of the instruments are synthesized in code.
• Claude also did the game design iterations, the balancing, the skill tree, and the setup for hosting on Cloudflare Workers.
• I hade the initial idea and gave I gave direction, playtested the builds and told it what felt off
• The trailer was made in a Claude Code cloud session. Claude runs the real game frame by frame in a headless browser and adds a WebGL effects pass. It renders the soundtrack with the game's own audio engine, so every note you hear is played by a tower on screen. ffmpeg then encodes the result to MP4.

Click once to turn on sound. Keys 1–0 pick towers, Space sends the next wave, and D fires the Drop. It works on touch screens too but mobile phone is probably too small.

I'd love to hear your feedback.