[As feature code tutorial 13] Greedy snake

Ideas:

1. First specify the Movement area width (stagew) and height of the snake (Stageh)

2. Increase the keyboard to listen, get the keying code, if the key and the previous key is reversed will not change

3. In the initialization, please note: The size of the snake head, snake body, food is 7 pixels

4. Each moving step (move) is 8 pixels in order to achieve the body of a lattice of the effect

5. After eating food, the length of the snake body is increased by 5 units, copying 5 bodies

6. Crawler forward: Starting from the tail, the last one to follow the position of the previous one, the first following the snake head

Icon:

1. The whole idea

2. Snake head, snake body, food size are 7 pixels, step 8 pixels