I’ll just chime in with my knowledge of pushing Harlowe beyond its limits…
Harlowe: thinking outside the (box:)
If what I’ve described (in that dump of technical babble) doesn’t resonate with you, then SugarCube is most likely a better choice.
Edit: Upon looking more at Figma, it looks like it might be generating some SVG behind the scenes. There is an SVG export function. SVG works well in practically all browsers. There seems to be some CSS export ability, but that’s for you to work through… 
Exporting CSS Code - Figma Handbook - Design+Code
SVG can be styled by CSS, just FYI. I’m familiar with both so let us know if you have any specific questions about exporting from Figma once you’ve made some headway.