Sure, 2048 isn't a challenging, action-packed, adventure through a magical land, but it's absolutely addicting none the less. Somehow, though, Pokémon 2048 makes the whole experience even better. In Pokémon 2048 you add PokéDex numbers for Pokémon together instead of regular old numerals, and it's just amazing.
You start out Pokémon 2048 with Ivysaur, Pokémon #2 in the PokéDex. Add two Ivysaurs together, and you get a Charmander, which is Pokémon #4 in the PokéDex. Add two Charmander together, and you get a Wartortle, two Wartortle get you a Pidgey, and so on. Not only is Pokémon 2048 a fun way to pass the time, but it will also improve your knowledge of PokéDex numbers, and that's always useful.
There are multiple free versions of Pokémon 2048, but I prefer this one on Github. You can play it either in a browser on PC or a smartphone browser where it works equally well.