Consider adding helpful features in poster visualization view

[irapha]

When browsing through posters in the visualizer, it is currently hard to know whether you've checked something out already or not. In particular, when trying to decide which posters to click, it's not easy to "mark as seen" to indicate that a given dot was acknowledged, but that I decided I'm not interested in it.

This could be done in a variety of ways. Off the top of my head, one option would be to "right click" to mark as read, which will change the color of the dot to indicate it was been "read"

Another unrelated feature that will be nice to have is a grid underneath the visualization, which would alleviate the problem of not knowing which dots I've already hovered over and which ones need my attention.