Daily mind stretches
Over the summer, a friend turned me onto these little ditties. Pattern recognition puzzles.
daily set games
I found them challenging and fun. Easy to get into flow with and easy to get out and onto to something like work. After getting the hang of it, I noticed my brain shifting and going into some other mode. Much of the time it's engaged with language-based activities or activities that have some language component. Here it's purely visually-based patterns. I haven't tried out any of the others and I've since abandoned this one too. Not much of a puzzler...