help please

1. When setting the offset for a projectile, is it possible to set the offset based on the center of the screen, as opposed to based on character location.

2. How would I add a series of sprites which i intend to play as a sort of flip book movie sequence which would cover the entire screen?

1. For a MUGEN Helper-based projectile:
postype = left or right
=> left: Interprets off_x relative to the left edge of the screen. A positive off_x is toward the right of the screen.
=> right: Interprets off_x relative to the right edge of the screen. A positive off_x is toward the right of the screen.
Also, Helper-based projectile (helpertype = normal) is basically a MUGEN player so you can use most MUGEN state controllers like PosAdd/PosFreeze/PosSet/Offset/Width..etc. to manage its positions.
But, at the same time you need to take care of some MUGEN Helper issues such as the weirdness of being put into custom state by your MUGEN Enemy...

2. Suppose your "flip book" sprites are 640x480 in dimension sizes.  Add the sprites in your MUGEN .sff file with x-axis = 320 and y-axis = 240.  Make a MUGEN animation (i.e. [Begin Action 888]) out of them with your perferred animation frames times in your MUGEN .air file.  Then in your MUGEN .cns file, make a MUGEN "flip book" Helper with a blank animation (i.e. add a [Begin Action 99999] -1,0, 0,0, -1 to your MUGEN .air file).  Call the made MUGEN "flip book" Helper with "helpertype = normal" and "pos = 160,-120" and "postype = left".  Then in the made MUGEN "flip book" Helper state, give it the "anim = 99999" and at its state Time = 0, make a MUGEN Explod with "anim = 888" and "pos = 160,120" and "postype = left" and "bindtime = -1" and "scale = 0.5,0.5" and "ontop = 1" and "ownpal = 1".  Remember to use ModifyExplod and DestroySelf to end the MUGEN "flip book" Helper and its MUGEN Explod according to your own MUGEN conditions.