difficult to tell due to the perspective but the line represents the player's hitbox and it can detect when the player (represented by a 3d point) is a certain distance away from a shape and react accordingly

and of course the size of the hitbox will be able to be changed along both axises, I'm not sure whether I'll make the shape of the hitbox changeable or not (for stuff like vehicles, but the thing about those is that you could make them a physics object instead of like changing the player hitbox so idk)