Moving Sammy the snake
So, we have Sammy the snake on the screen, sitting there, looking snaky. However, it isn't much of a game. If it were, we could finish the book right here! What we need to do now is get that snake slithering across the screen!
First, let's sort out the playing area. Currently, the resolution is 640 x 480 pixels and the snake texture is 32 x 32. This means we have a grid of 20 x 15—derived by dividing up the resolution by the texture (640/32 = 20, 480/32 = 15)— of the different positions the snake head could be in. The reason we are going to do it this way is because the original game moved with a periodic movement of one snake component at a time. We are going to do the same.
Let's define our timer. We are going to start off ...