Okay, so what if you set it up so that while slide boolean is true > every frame the player is under the wall the deceleration is set to 0 or 1 (or something really low) > else deceleration set to whatever you have it set at now, so that they move at constant speed until the end of the wall and then begin to decelerate on leaving?
Haven't tested, but just spitballing ideas
Right, but how will I identify that there is a wall just above the player's character?
C2 has two routines to identify ground below the player (Platform is on floor) and walls next to him (Platform has wall to left or right), but dont have to something above it.'