I recently revisited Monument Valley & Monument Valley 2. I played them both when they originally came out in 2014 & 2017 respectively. They are now both available on Apple Arcade (as Monument Valley+ and Monument Valley 2+).
Both games are puzzle games by Ustwo Games. They present the levels with optical illusion effects. These optical illusions remind me of M.C. Esher's Impossible Constructions.
These games are beautiful. The soundtracks are great too. I think Ustwo really nailed it artistically with these games.
Each level is almost the perfect length. The levels are not too difficult either. I was able to complete a level or two quickly while waiting around. If I wanted to, I could binge multiple levels quickly.

There were two expansion packs released for Monument Valley. Those were "Forgotten Shores" and "Ida's Dream". "Ida's Dream" was a limited-time promotion part of Apple's Apps for Red initiative.
Monument Valley 2 released an extra chapter after release called "The Lost Forest". It was a much shorter expansion and was free to everyone.
The Apple Arcade version of these games includes all of the extra content.
These games are both perfect on mobile. Not too difficult, short levels. I can pickup the game at any time. I wish that there were more games like this. I think games now are more interested in keeping you in a game and spending money. Monument Valley and Monument Valley 2 told stories and didn't try to hold you hostage.
I've read that Ustwo is currently working on a Monument Valley 3. I hope that's the case.
I had a great time revisiting these games. I'll probably do this again.
Both games are also available on PC (Steam) in the Panoramic Collection.