Nauč se Python > Materiály > Snake Workshop for PyLadies > Extensions > Snake extension: Infinite playground

This is a machine-generated translation.

# Infinite cage #

Instead of ending the game when hitting the edge of the window, you can let the snake "pass through" and appear on the other side.

From a game logic standpoint, it's not as complicated as it may sound. It's enough to set the appropriate value for the end of the game in the `move` function. However, it's necessary to be careful where to use `new_x` and where to use `new_y`, where to use `width` and where to use `height`, and where to add or subtract one, so that everything fits when numbering from zero. Give it a try!

### Řešení

However, if you draw a snake (instead of a caterpillar), you will now encounter a problem with selecting the correct pieces - the edge of the snake game visually divides it into two smaller parts. I leave the solution to this problem to the reader - with the note that it is a very difficult problem.

## Residual solution #

Can the logic of climbing out of the window be solved more simply? Yes, it can! Mathematicians have come up with an operation called the remainder of division. It does exactly what you need - the remainder of division of the new coordinates by the size of the field gives a coordinate that lies within the field. When the previous coordinate was one larger than the maximum, the remainder of division will be zero; when it was -1, we get the maximum.

Python uses the operator `%` for the remainder after division. Try it out.

``````>>> 6 % 10      # Remainder after dividing six by ten
6
>>> 10 % 10
0
>>> -1 % 10
9``````

The entire code for controlling and handling climbing out of the playing area can be replaced by two lines.

```new_x = new_x % self.width
new_y = new_y % self.height
```

Similar mathematical 'shortcuts' can often make life easier for programmers. However, coming up with them is not always easy. But don't worry: if you're not interested in studying computer science at school, know that it's possible to do it without 'shortcuts'. It just might be a bit more convoluted at times.

The fact that there is exactly the operation we need is not entirely a coincidence. The mathematical simplicity is rather the reason why the playing field behaves this way in many old games. <This is called toroidal topology in professional terms.

For mathematicians

Experienced mathematicians may now complain about the need to define the remainder of division of a negative number. Therefore, I will add that Python intentionally defines it appropriately for this purpose; `a % b` always has the same sign as `b`.

## Rendering #

In your free time, try to fix the problem. I recommend returning to the 'abstract' function that only prints coordinates and directions:

``````1 2 tail right
2 2 left right
3 2 left top
3 3 bottom top
3 4 bottom top
3 5 bottom right
If you follow the instructions, you have this function saved in the file `smery.py`. First, fix it and then 'transplant' the solution into the game.