====== Star Battle Expanded Pattern ======

//Star Battle// uses the [[hardware:magic system#Magic Register]]'s [[hardware:magic system#expander|Expander]] function to pack its fighter patterns in half the ROM space. The XOR function 'merges' the fighter with the background.

<code z80>

; XPAND load (code portions omitted for clarity)
; [...]
L2650:    LD      A,$08         
          OUT     ($19),A       ; write 00001000B to XPAND (foreground color = 10, background = 00)
          
; [...]

SYSSUK  WRITP                   ;  UPI WRITe with Pattern size lookup
          DB      $7C           ;  ... X = 124
          DB      $00           ;  ... Y = 0
          DB      $28           ;  ... Magic Register = 0010 1000B (XOR, Expand)
          DW      $26EC         ;  ... Pattern Address
          
; [...]

; Small H-Fighter Graphic
L26EC:    DB    10000100B            ;   X . . . . X . .
          DB    10110100B            ;   X . X X . X . .
          DB    11111100B            ;   X X X X X X . .
          DB    10110100B            ;   X . X X . X . .
          DB    10000100B            ;   X . . . . X . .
          
; [...]
</code>