Ok, thanks, perfect, i understand now and i just succeeded in doing it.

now that i know the solution, it looks logical, but if i hadn't read an answer like yours, I wouldn't have found the solution for sure :s (that's why i'm a noob :|)

ps : indeed, this is a map entity, which is normal for a door i guess :Y

edit : i watched the video of your game some days ago, and it looks damn pro :s