Flappy Bird is a great starting game. It has a clear objective, uses much of the Scratch functionality, is relatively simple to create, and you can use your imagination by drawing your own sprites, backgrounds, and pipes.
What kind of a game is Flappy Bird? It is a game where your goal is to keep on pressing a button to make a bird rise as it is constantly falling while navigating its way through the pipes of varying heights that are coming at it.
It can be broken down as follows:
Every button press makes the bird go up on the y axis
Every second the button isn't pressed the bird goes down the y axis
A pipe starts at the right end of the x axis and moves left toward the bird
When the pipe reaches the far left corner without touching the bird, you earn a point and the pipe disappears
If the bird touches the ground...