Shifting screen maze help

[Travveh]

OK, I've got the maze working fine and all, but I have a couple little things I want to add, but can't figure out without ruining the entire thing.

1) I want the character to leave a trail behind it that will stay when I revisit that screen (currently it just clears it when you switch screens (to make it work properly, just add 'offscreenonly' to the first line of the program and uncomment cls))
2) On walls that are from 0 to 1 on the y-axis you can go through them horizontally.
3) After just going to another screen, when posY = 0 then you can go through the walls and go all the way across the screen.

If you find any other glitches, missing walls, etc. do tell.
Thanks.

[Travveh]

Fixed a small bug... Little error on my part... left out the trail on this d/l though. And added... flashiness at the end.