Try it like this:- ; 10 SYS (5120) *=$1001 BYTE $0E, $10, $0A, $00, $9E, $20, $28, $35, $31, $32, $30, $29, $00, $00, $00 MAP = [start of map data] SCRN = 7680 *=$1400 jsr defchr jsr drawmap rts defchr ; redefine char memory lda #255 sta $9005 rts drawmap lda #<SCRN sta $fb lda #>SCRN sta $fc lda #<...