I dont understand what the teacher is doing.

Hi there, Justus Aberson!

Yes, I can see why you’re confused. The video quickly glossed over the fact that he’s focusing on the 2,2 coordinate position. This is where your “tower” in the game will be positioned.

Because positioning is so important to be able to hit your attacking enemies, we need to make sure we use the center point (2,2) as our anchor.

Remember, we set the range (the reliable distance the tower can defend and hit enemies from) as 1.

func points(inRange range: Int = 1)

This corresponds with the grid-spacing shown in the video. (We can only hit enemies within 1 grid space away.)

2,2 (x,y) - [This is where our tower is positioned.]

Another important note: All of the X-coordinates are the same. And all of the Y-coordinates are the same. [See images below in this answer.]

Meaning, we can subtract 1 from the X-coordinate in the center position (2,2) and reach all of the “lowerBounds” for the enemies that choose to attack from there:

(2, ) - 1 = (1, )

(1, ) (1, ) (1, )

And we can add 1 to the X position to reach the enemies in the “upperBounds”.

(2, ) + 1 = (3, )

(3, ) (3, ) (3, )

Same for the Y-coordinates.

( ,2) - 1 = ( ,1)

( ,1) ( ,1) ( ,1)

( ,2) + 1 = ( ,3)

( ,3) ( ,3) ( ,3)