anchor.diff:      (as/until :negative (bita (mem +ppu-status+))) ; PPU warmup interval
       (as/until :negative (bita (mem +ppu-status+))) ; (two frames)
   
  -    (jsr 'player-init)
  -
  -    ;; Fill nametable.
  -    (lda (mem +ppu-status+))            ; Reset address latch..
  -    (ppuaddr #x2000)
  -    (jsr 'fill-nametable)
  -    (lda (mem +ppu-status+))            ; "                   "
  -    (ppuaddr #x2400)
  -    (jsr 'fill-nametable)
  -
  -    ;; Fill attribute table.
  -    (lda (mem +ppu-status+))            ; Reset address latch..
  -    (ppuaddr #x23C0)
  -    (ldy (imm 0))
  -    (lda (imm #b01010101))
  -    (jsr 'fill-attributes)
  -    (ppuaddr #x27C0)
  -    (ldy (imm #b10101010))
  -    (lda (imm #b11111111))
  -    (jsr 'fill-attributes)
  -
  -    ;; Program palette.
  -    (ppuaddr #x3F00)
  -    (dolist (color '(#x3F #x2D #x3D #x30  #x3F #x03 #x13 #x23
  -                     #x3F #x2D #x3D #x30  #x3F #x05 #x15 #x25
  -                     #x3F #x3F #x27 #x37))
  -      (poke color +vram-io+))
  +    ;; Paranoid initialization. Had some intermittent quicks on real
  +    ;; hardware, as though the nametables weren't fully initialized,
  +    ;; so I've inserted a bunch of paranoid vblank syncs, and call the
  +    ;; init routine multiple times just to be sure.
  +    (lda (imm 3))
  +    (sta countdown)
  +    (as/until :zero
  +      (jsr 'init-nametable)
  +      (jsr 'init-attr)
  +      (jsr 'init-palette)
  +      (dec countdown))
  +
  +    (jsr 'player-init)                  ; Initialize music player
   
       (lda (imm 64))                      ; Initialize scroll variables
       (sta scroll-x)
  
positive.code:     (jsr 'update-sprites)
  
      ;; Switch pattern tables mid-frame:
      (emit-delay (+ (* 114 107) 30))
      (lda top-ntaddr)
      (eor (imm #b10010000))            ; Invert pattern bank.
      (sta (mem +ppu-cr1+))
  
negative.code:     (ldx (imm #xFF))                    ; Set stack pointer
      (txs)
  
      ;; Init sound hardware
      (poke 0 #x4015)                     ; Silence all channels
      (poke #x40 #x4017)                  ; Disable IRQ !!
  