Scratch

Scrolling X position and Y position
First make a variable named ScrollX and a other one called ScrollY
Make a character sprite with the following scripts

<when[ Up ]key pressed>
<change{ ScrollY }by( -10

<when[ Down ]key pressed>
<change{ ScrollY }by( 10

<when[ Right ]key pressed>
<change{ ScrollX }by( -10

<when[ Left ]key pressed>
<change{ ScrollX }by( 10

While making these scripts you can change how fast you want your character to scroll by changing the 10 on the scripts to whatever number you like.

Next make a sprite called terrain 0
with the following script


<when green flag clicked>
<forever>
<set x to( (( < { ScrollX }> <+> (( 460 <*> 0 )) ))
<set y to( (( < { ScrollY }> <+> (( 360 <*> 0 )) ))

Next make a sprite called terrain 1
with the script

<when green flag clicked>
<forever>
<set x to( (( < { ScrollX }> <+> (( 460 <*> 0 )) ))
<set y to( (( < { ScrollY }> <+> (( 360 <*> 0 )) ))

The zeros at the top could be edited to -1 , 1 anything and thats the  X and Y pos of the sprite.

If you dont understand download this game and check the sprites
http://scratch.mit.edu/projects/Reamm/633116