Collision?

i made collision in one of my other games, but i could back through the wall, so i tried to copy dameria's maze game collision. but it's not working... i don't understand why it does not move correctly and sometimes it does not even move at all and i'm still able to walk through walls...

I had a similiar problem... I couldnt figure it out so I gave up!

please help me on my question... http://www.alice.org/community/showthread.php?t=4494