I would like a slide-in box added to my site that is triggered on mobile only, when someone scrolls down to a certain level of each post, something like 70% of the way down, to help keep them engaged and on the site.
Optin Monster does a lot, so I thought that it would be a heavy plugin to use? I wanted to see if there was anything you guys have used or recommended for just specifically a slide-in related post box.