There is a millennium-old game "that works", which is called "meditation". There are many versions, some nonsensical (tantric) and some not (so-called Raja Yoga, Zendo, etc).
> “It’s the first real attempt to meaningfully harness the power of games in a dedicated cognitive enhancement tool,” commented C. Shawn Green, a neuroscientist at the University of Wisconsin-Madison and experts on brain training<p>This statement is an exaggeration. Games based on N-Back and Dual N-Back were first introduced in 1958 and 2003, depending on how you count.<p><a href="https://en.wikipedia.org/wiki/N-back" rel="nofollow">https://en.wikipedia.org/wiki/N-back</a>
It's also interesting to listen to the episode of The Tim Ferriss Show [1] where T. F. and Adam Gazzaley talk about this topic - how to enhance cognitive functions via games etc.<p>[1] <a href="http://fourhourworkweek.com/2015/06/22/adam-gazzaley/" rel="nofollow">http://fourhourworkweek.com/2015/06/22/adam-gazzaley/</a>
This is stupid, I know, but I recommend playing one of those boring looking simulator games.<p>Focus for one hour doing nothing but driving a train from point A to point B. Fly a plane around. Plough a field. Very zen.
One of my favorite books on the subject is Shunryu Suzuki's "Zen Mind, Beginner's Mind" (<a href="https://en.wikipedia.org/wiki/Zen_Mind,_Beginner%27s_Mind" rel="nofollow">https://en.wikipedia.org/wiki/Zen_Mind,_Beginner%27s_Mind</a>).