-Click the button adds an overlay on each Activity case, and adds a message at the bottom "Activity Settings".
-In this case, clicking on an Activity case brings to its Settings page.
-Else, clicking again on the button return to normal Activity selection mode. I think the icon and color outline will make it easy to understand.
(note, I added a flat green with gradient for the bottom text area as a quick edit, but of course we should just make the bottom of the activities grid higher and keep the main background).