For https://skilldrick.github.io/easy6502/

easy6502_burger_wip-fill.asm

; Burger pieces:
;  #$00 - nothing             Keys:
;  #$01 - bottom bread A      1: bottom bread
;  #$02 - bottom bread B      2: sauce
;  #$03 - sauce               3: lettuce
;  #$04 - lettuce             4: tomato
;  #$05 - tomato              5: patty
;  #$06 - patty A             6: cheese
;  #$07 - patty B             7: top bread
;  #$08 - cheese
;  #$09 - top bread A
;  #$0a - top bread B         0: remove piece

Init:
 ; Colors
 LDA #$0e          ; ╮ $00 BG color
 STA $00           ; ╯
 LDA #$08          ; ╮ $01 Bread color
 STA $01           ; ╯
 LDA #$0a          ; ╮ $03 Sauce color
 STA $03           ; ╯
 LDA #$0d          ; ╮ $04 Lettuce color
 STA $04           ; ╯
 LDA #$02          ; ╮ $05 Tomato color
 STA $05           ; ╯
 LDA #$09          ; ╮ $06 Patty color
 STA $06           ; ╯
 LDA #$07          ; ╮ $08 Cheese color
 STA $08           ; ╯

 ; Stack
 ; ...

StoreGraphics:
 ; Bottom Bread A
 ; Bottom Bread B
 ; Sauce
 ; Lettuce
 ; Tomato
 ; Patty A
 ; Patty B
 ; Cheese
 ; Top Bread A
 ; Top Bread B

FillBG_init:
 LDA #$02          ; ╮ X/$11: Drawing page/high byte
 TAX               ; ╯
 LDA #$00          ; ╮ Y: Drawing position
 TAY               ; ╯
 LDA $00           ; Load background color into A
FillBG_loop:
 STX $11           ; ╮ Draw background color pixel
 STA ($10),Y       ; ╯ to screen using indirect addrs.
 INY               ; Increment screen position
 CPY #$00          ; ╮ Check if Y has overflowed,
 BNE FillBG_loop   ; ╯ otherwise loop.
 INX               ; Increment page
 CPX #$06          ; ╮ Check if X passed enough pages,
 BNE FillBG_loop   ; ╯ otherwise loop.

DrawBurger:
 ; Pen on/pen off technique for 1-bit graphics
 ; ...

PollInput:
 ; ...

UpdateStack:
 ; ...

BRK ; Debug
 JMP DrawBurger