Whats Wrong HELP

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Whats Wrong HELP

I wrote this program which is supposed to be like etch a sketch ..
but for some reason it wont go more than a few pixels left....can
some1 help....


#include "ti-85.h"
.org 0
.db "By Frank Apap",0


X = $80E0                   ;X in mem
Y = $80E1                   ; Y in mem
Init:
 ld a,4
 out (5),a
 ROM_CALL(CLEARLCD)
 ld a,30                   ; x start
 ld (X),a
 ld a,60                   ; y start
 ld (Y),a


Start:
    call GET_KEY   ; get a key
    cp K_UP
    CALL_Z(up)
    cp K_DOWN
    CALL_Z(down)
    cp K_LEFT
    CALL_Z(left)
    cp K_RIGHT
    CALL_Z(right)
    cp 0F
    JUMP_Z(clear)
    cp $37
    JUMP_Z(exit)
    jr Start
up:
  ld a,(X)  ; x=x+1
  inc a
  ld (X),a
  CALL_(PlotPixel) ; draw it
  ret


down:
     ld a,(X)
     dec a
     ld (X),a ; x=x-1
     CALL_(PlotPixel)
     ret


right:
  ld a,(Y)  ; y=y+1
  inc a
  ld (Y),a
  CALL_(PlotPixel) ; draw it
  ret    ; go back


left:
  ld a,(Y)                           \
  dec a                               \
  ld (Y),a                             >  IS SOMETHING WRONG?
  CALL_(PlotPixel) ; draw it          /
  ret   ; go back                    /


clear:


    ROM_CALL(CLEARLCD)
    JUMP_(init)


PlotPixel:
    ld a,(Y) ; LOAD Y into B
    ld b,a
    ld a,(X)  ; LOAD X into C
    ld c,a
    ROM_CALL(FIND_PIXEL)
    ld de,$FC00
    add hl,de
    or (HL)
    ld (HL),a
    ret


exit:


     ROM_CALL(CLEARLCD)
     ld hl,$1A1A
     ld ($8333), hl
     ld hl, (PROGRAM_ADDR)
     ld de,bye
     add hl,de
     ROM_CALL(D_ZM_STR)
exitloop:
   call GET_KEY
   cp $37
   ret z
   jr nz,exitloop


bye: .db "BYE THANKS FOR TESTING",0
.end