The check-in game is one of my favorites, and it's pretty much the first thing I introduce to all my students. It's super simple to play, and can be adapted to all sorts of situations and challenge-levels.
Most importantly, the game teaches your dog the value of auto-check-ins, which is when they look at you without you prompting them to do so. Auto-check-ins are one of the most important skills for successful leash walks, decompression walks, off-leash adventures, reactivity training, and more.
Check out the video demo, and take a look at the written guide if you'd like even more details on how to introduce and develop the game.
PS: Outside of the context of playing the check-in game, be on the look-out for those everyday life auto-check-ins. Maybe your dog looks up at you on a walk, or they check in when they see something they're unsure about. If you're in a situation where you'd like your dog to be seeking contact with you more frequently, REWARD it when it happens!