Crypt of the Necrodancer.
Really fun roguelike game where you and enemies have to move to the beat of that floor's song. I think part of the reason I still play it a lot is that it's amenable to very short sessions. I've played enough that runs go fast and I either clear or die within 10 minutes.
Over 1200 hours now almost a decade after release, and a huge chunk of that is probably sessions of under 30 mins in length.