I remember answering this one around a year ago on another thread. I cannot find it now
But basically you want to use a ray cast to shoot in the direction of your grappling hook animation. See what the raycast hits. If it is valid hit (check the tag), also maybe check the distance. (If too far, cannot get it). Then get the position. With the position, depending on your type of character controller, move them towards that position. Maybe set your character transform, tween, or whatever method you want to use to move.
