Sirv's solution for single image hotspots is semi-developed.

It's not easy to:

• change the colour, size, opacity of the spot. 
• adjust the styling of the tooltip or message box.
• The configuration can't be saved in a file in your Sirv account (it can for spins but not images), so there's no way to go back and edit your settings visually.

We will build all these things once we've finished building the spin hotspot editor. 

It'll be really cool once built, but for now it needs a lot of effort to get good results, unless you're happy with the default styling of spots and messages.

• https://tools.sirv.com/image-hotspots/
• https://sirv.com/help/articles/hotspots-on-image-api/