Diep.io vs Flappy Bird
Diep.io
Diep.io is a fun tank-like IO game where players play as pencil-drawn tanks on a piece of white (and sometimes gridded) paper filled with other hostile tanks as well as a variety of obstacles and Polygons. Shooting at Polygons and other players will earn you points to level up your tank to the next tier, unlocking a wide range of upgrades (or "classes" as the game calls them). At frequent intervals, AI-controlled bosses will be spawned allowing players to work somewhat cooperatively to earn a ton of experience points.Many players are calling out Diep.io as being a clone of the previously popular Tank.io (not sure what happened to Tank.io though), but considering that it's currently the last game standing, I guess it's safe to say that new players will never know about Tank.io but will instead be able to enjoy its legacy through Diep.io.
Flappy Bird
Flappy Bird is one of the most infamous hypercasual games out there. In this game, you need to help the flappy bird make its way through the sky that, for some reason, is covered in green pipes that resemble the ones in the iconic arcade-platformer, Mario.The game was designed to be insanely-easy to pick up - after all, you only need to tap or click to keep the bird afloat. However, playing the game can literally drive you insane with frustration because of how difficult it is. Needless to say, you'll see the "game over" screen a lot more than you'd like to within the couple of minutes you spent in the game... and that's a fact.
Flappy Bird, along with multiple of popular mobile games, helped paved the way for an entirely new genre of games to emerge. The game is definitely more than the hundreds of memes it gave rise to.