The mechanics are very simple: you have to tap on the screen to make the doge fly, trying to keep the rhythm stable so that it flies through the pipes scattered across the screen, something that is very difficult to do.
It will be a challenge to get more than five points (by passing through five pipes), as it is very difficult to keep a steady rhythm. In fact, you will have to practice a lot before you start doing well and the game stops being so frustrating.
Each time you crash and start again you will see some slight differences that make it so the game isn't so monotonous. You will play in different scenes, at different times (day or night) and with different colored 'doges.'
Flappy Doge is an arcade game with very simple mechanics, which presents quite a challenge. This is precisely why it's so successful, because it is able to suck you in with just the right difficulty level to make you want to keep trying one more time.
Requires Android 2.2 or later.