The first time you tap on the “Get Ready” screen, Flappy (assuming it is its name) jumps immediately. Instant feedback.
Once you do that first tap, Flappy drops quickly, urging you to tap again and find your rhythm.
The game over screen does many things right at once. The empty medal intrigues. The score and best score field constantly urge you to try again.
It only takes two taps from the Game Over screen to be playing again. One second, or less.
It only takes less than four seconds from playing to the first pipe.
The variation in pipe heights never seem impossible.
The art style immediately charms you, as the style is likely already impressed into your subconsciousness for years and years as part of Super Mario Bros, one of the most popular video games ever (so popular that I feel a little silly having to mention its name).