Check out some problems from the MODS POTD here. Use Shift+Click to highlight a problem you've done, and Ctrl+Click to 'star' a problem with a different color. This was meant to be a 'secret' page since going into the problem displays what I was thinking while solving the problem, my solution, and the "idea" I found interesting behind that problem, but I think it's for the above reasons that I should just make it public.