 ldx #<reverse_font_table 
  ldy #>reverse_font_table
  stx temp_ptr_x
  sty temp_ptr_x+1
  
; copy font        
  ldx #$04      ; copy 4 pages = 1KB
  ldy #$00      
:
  lda (temp_ptr_z),y
  sta (temp_ptr_y),y
  eor #$ff      ; reverse char
  sta (temp_ptr_x),y
  iny
  bne :-
  ; switch to next page
  inc temp_ptr_z+1
  inc temp_ptr_y+1
  inc temp_ptr_x+1
  dex
  bne :-
  
; enable font
  lda $d018
  and #$f1
  ora #$09
  sta $d018
  cli
  rts


.rodata
font_attribute_table: