Player_Position is a variable whitch controls Player.X position.
In r57, when player_detector collide with Blocker_Left it moves player to a new position, and screen scrolls to a new position as well - pretty straight forward.
but in r58 look's like collision is not triggered, player can overlapp or walk through blocker_detector and nothing happening :/
I didn't do or change anything after installing r58, just save project in r57, installed r58, open project in r58, that's it :(