Short Action side scroller (Rescue) WIP

Hi,
Heres the problem, this game in sections is a side scroller, and becouse of all my rounded objects the character ceps sliding off the stage. Can eny1 tell me how to only make the player move along the x and z axis’s. Also i want a crossbow shooting feature, when u press z a mouse controlled crosshair shows up and is controles the players aim(can only aim whils standing still), if some1 could point me in the direction of a useful relevent python script id be verygreatfull.
Heres the blend:
http://www.megaupload.com/?d=PWLX5BMJ
:smiley: Please help
http://file043a.bebo.com/7/large/2008/08/08/12/3745344149a8574635304l.jpg
Rescue , is a game set in a future in a different reality , 1 in whitch the people never saw the appele in gunz , eather that or they never thought of making them, (leavind all the weapons medevil and awsome!!!
You play as Sasha, the female hero who is on a mission to save her freinds from the Boss.

Again please help

You do not need Python for this. Simply use the Constraint Actuator and set it to the acceptable range of movement on the Y axis.

BTW, I’m looking forward to seeing your progress. Your screenshot looks great!