halloween.js

Install guide · AI assistant

Add Halloween effects with an AI assistant

Ask your AI coding assistant to do the install. It reads a SKILL.md file that lists every class, option and gotcha of halloween.js, so it knows where to add the code and how to keep it working.

Steps

  1. Open your project in an AI coding assistant that can edit files and read web pages, such as Claude Code or Codex.

  2. Paste the prompt below.

  3. Review the change the assistant proposes and publish it as you normally would.

The prompt

The assistant reads SKILL.md, which lists every class, option and gotcha, and then edits your project. 

Add Halloween effects to this website using halloween.js. Follow the instructions at https://halloween.js.org/SKILL.md. Leave the script in the site after installing it: it switches itself on every year from 18 October to 2 November and off again.

Install once, then leave it. The effects switch on by themselves every year from 18 October to 2 November and stay off the rest of the time. There is nothing to remove afterwards. Installed earlier? You will see nothing until 18 October. That is expected, not a bug.

Check that it works

  1. Open your live site in a private window and reload without cache.

  2. Between 18 October and 2 November you should see webs in the screen corners and eyes blinking within a few seconds. Outside those dates the page looks unchanged.

Good to know

  • Want to test outside the season? Open the playground, set the active season to cover today and copy the snippet it generates.
  • Ambient effects stop when a visitor has reduced motion turned on. The screen-corner webs stay.
  • The effects sit in a fixed layer and never shift your page layout.
  • No web access in your assistant? Download SKILL.md, add it to the project, and tell the assistant to follow that file. In Claude Code you can save it as .claude/skills/halloween/SKILL.md to make it a skill.
  • The prompt asks the assistant to leave the script in place. That is intentional: the season window turns the effects on and off by itself every year.
  • Nothing showing in season? See troubleshooting.