Show HN: Free tool to mark points and polygon regions

For a game I'm developing I needed an easy way to create hotspot areas on images. So I hacked together a small tool to do so and before I knew it, I had created an entire app :-) It allows you to generate JSON or YAML from the coordinates you tack on the image. tack runs entirely in your browser, there is no server side component to it, so good in terms of privacy. Hope this is helpful.