Doodle Jump was one of the App Store's earliest genuine phenomena, and it's a small masterpiece of control design. You tilt the phone to steer and the character jumps automatically. That's the entire input scheme, and it made the game playable one-handed on a bus.
The aesthetic did as much as the mechanics. Everything looks drawn in biro on graph paper, which meant the developers could add anything - UFOs, black holes, ninjas, monsters - without breaking the visual logic. It's a sketchbook, so nothing is out of place.
The endless vertical structure was still fairly novel in 2009. There's no level and no win condition, just a height and the certainty that you will eventually miss a platform.
The little squeaks and the pencil-scratch sound design are burned into a whole generation's memory.
This collection covers the Doodler and its obstacles.