It can happen if your collision code relies on exact positions. Since you use physics, the character can move several pixels at a time and that's your issue.

Yeah this is why in some ultra rare occasions and if you're good enough, it is possible to go through two blocks placed diagonally in Super Sonic Ball. I only had this happen once, though, and I remained stuck in the block for like 30 seconds before I managed to get on the other side.

By the way this looks nice .

Isn't that kinda slow, though?

could you explain it in axe code please?
because i tried different things but they didn't work

anyways as you can see in the screenie the character still goes offscreeen sometimes, can someone explain to me why this happens?

yeah i've had that issue before.
i noticed that you can only pass through the walls if both arrow keys are pressed if you approach the wall

With physics, you can't rely on button presses for collisions with the character sliding around. Since the character can only move one pixel at a time the fix is easy, keep your acceleration cap where its at, if it can accelerate at 2 or more pixels checking it will be slower.

Here's your line of code for testing wall collisions:
if ((ptest(x/256-1,y/256+1) or ptest(x/256-1,y/256+7)) and not (gkey(3))) xor ((ptest(x/256+7,y/256+1) or ptest(x/256+7,y/256+7)) and not (gkey(2)))
*I don't think you meant to put the xor in there!  

Change it to this:
if ((ptest(x/256-1,y/256+1) or ptest(x/256-1,y/256+7)) and (A<<0)) or ((ptest(x/256+7,y/256+1) or ptest(x/256+7,y/256+7)) and (A>>0))
Basically, if a wall is to the left or right of the character, stop him if hes going to accelerate past it.  

looking nice!
And check if your character positions are similar to the picup thingy positions i guess.

well shit...
after a random ram clear, i've lost my whole code  :'(

now i'm looking at the code i've posted and it's a little bit messy.
could anyone please optimize it for me?
it would be highly appreciated!