I’d highly recommend investing the time to learn and master Axure. It’s less shiny and nice-looking than Sketch (or the other 100 apps that do what Sketch does), but Axure has the capability to build in interactions without extra plugins, and you can preview the interactions really quick. Simply put, it’s WAY more powerful than all those other apps in terms of building a prototype that communicates a visual or interactive idea.
Axure also does a good job at speaking in terms of CSS without forcing you to code. You get familiar with click events and transition css just from looking at the options that it allows you to apply.