The AI example is using the stock movement actions (forces) to move the AI objects, I don’t think any physics engine involved in the actual calculations but I can be wrong. But in case you plan to make more advanced AI, you probably better off with pathfinding,
I would be more than happy to explain how to make an AI but you just mentioned before too much text may confuse you
And I can be very confusing even if english is your first language
So, I’m not sure if it worth the time to explain in detail how the AI works or how to make one.
It is not that simple really, if you are new to game development in general, you may need to get familiar with different concepts first to get the idea.
But let me try to explain the example in a simple way:
In the example each enemy constantly shooting the “view” object toward the player. If the ‘view’ object is in collision with the player it means, the player is visible to the enemy. If the ‘view’ object is in collision with an obstacle, the ‘view’ object get destroyed and so, if the player is behind the obstacle, the player is not going to be visible to the enemy simply because it is not colliding with the ‘view’ object.
If the player is visible to the enemy, the enemy get alerted using a variable. Object linking helps with the decision which enemy get alerted, which enemy can see the player. (I can explain in detail how object linking works but let see first if you understand the basic concept)
If an enemy is alerted because the player is visible to it, the enemy simply start moving toward the player and that’s it. After some time, if the enemy can not see the player any longer, it is going to stop.
Finally, if the enemy and the player is in collision with the obstacle the example is using the separate two objects event to simply keep the enemy and the player away from the obstacle.