How to create the game like Flappy Bird?

Flappy Bird, another popular game based on the 'simplicity', topped the chart not only in the Apple App Store, but also the Google Play Store before it was removed.

From the perspectives of the game play experience, the Flappy Bird is designed to challenge the consistency of the distance judgement of the players, with very high accuracy. Only 1 Hit Point, one highscore and infinite tries, no Mana Point, no magic, no checkpoint, no multiplayer.

From the views of the game development, the Flappy Bird simply relies on the gravity for the movement, and a simple collision detection while the background is moving at a linear speed.

To be honest, I have no idea why this game becomes so popular, other than the 'simplicity'. And yes, after the tutorial on the Match 3 Game last time, here i would like to create this similar game myself, out of the curiosity. To summarize, i divide the game algorithms into several parts:

a) Flappy Bird Game Algorithm Part 1 - Gravity and flying

•  Alright, no box2d or other libraries. Only a few lines of codes will do.

b) Flappy Bird Game Algorithm Part 2 - Background movement

• Is trivial as well. Just need a good image.

c) Flappy Bird Game Algorithm Part 3 - Collision Detection

• A simple algorithm used to detect the collision of the object with the tunnels/walls.

d) Flappy Bird Game Algorithm Part 4 - An Android Game Demo

• Apart from the basics, let's demo a self-customized version

Note:

• I would be using other images to replace the original Flappy Bird.
• The game requires the Adobe AIR 4.0. You need to upgrade it if prompted.