Dinosaur

The Dinosaur Game was never meant to be a real game, Chrome's engineers built it as an easter egg to fill the no-internet error screen, and it stuck around because a single jump button and a constantly accelerating desert turned out to be enough to hook people waiting for their Wi-Fi to come back.

Because the game's speed only ramps upward and never resets, the run doesn't get harder through smarter obstacles, it gets harder purely through less reaction time between identical ones, which makes rhythm more valuable than reflexes once the pace climbs high enough. Holding the jump slightly longer clears pterodactyls flying at head height, while a short tap suffices for ground-level cacti, mistiming which one you're facing is the most common way a long run ends abruptly. Flappy Bird tests the same one-button endurance instinct with a completely different rhythm.