I have been on a bit of a Qix kick lately.
https://en.wikipedia.org/wiki/Qix I first discovered this game in the early 80s on the Atari 400 and it has drawn me in time and again ever since.
The Lynx version is my favorite but I have lately been playing it on the 3DS virtual console of the GameBoy version. It is a unique experience playing a game that is traditionally so colorful in B&W. It adds a new level of challenge since it is much harder to tell when the Qix changes direction. Plus depending on your score you get Mario in some rather stereotypical costumes, varies depending on score.
List from:
http://www.nindb.net/gb/qix/index.html50,000-149,999pts: Mexico Mario
150,000-249,999pts: Africa Mario
250,000-299,999pts: Spain Mario
300,000-349,999pts: India Mario
350,000-399,999pts: China Mario
400,000-499,999pts: England Mario
500,000pts or more: Mario, Luigi, Peach and Toads in a castle
http://www.nindb.net/gb/qix/img/cameos/marioworld.png <--Image of all 7 of these
If you haven't played this game, I would suggest giving it a try. It is much like Tetris in that it lends itself equally well as something quick to kill a minute or two while standing in line or as an extended, nearly meditative, gaming session. It is available on a wide variety of platforms.
https://strategywiki.org/wiki/Qix/Versions