sethl2matrix:
 ld hl,matrix
 ld a,(y)
 inc a    ;djnz needs at least 1 else it loops over and that would be bad
 ld b,a
 ld a,(x)
 ld c,a   ; load a to c so we can
 xor a
_:
 add a,c
 djnz _
 ld c,a
 ld b,0
 add hl,bc  ; matrix pos stored in HL