Enemy sprite interaction with player's sight

[GuillemBarroso]

Enemy sprites will only be displayed once they enter the player's sight area.

If an enemy sprite exits the player's sight area, the enemy should still be displayed in the fog area. However, the image will not move even if the enemy does.

The player will not detect the enemy movement until it enters the sight area again.

While a previously detected enemy is not in the player's sight area, the image will be displayed, but it will tend to disappear. This denotes that this is not the actual position of the enemy.