gameboy rom to try clear screen in apa mode

clear.c

#include <gb/gb.h>
#include <gb/drawing.h>

void main()
{
  int x =0;
  int y =0;
  
  int clean = 0;
  
  UBYTE blankTile[] =
  { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
    0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
  };
  
  UWORD idx;
  
  //whoopty
  color(BLACK,BLACK,M_FILL);
  box(0,0,GRAPHICS_WIDTH-1,GRAPHICS_HEIGHT-1,M_FILL);
  
  while(1)
  {      
      UBYTE joy = joypad();
      if ( joy & J_A )//clear screen
      {
        if(clean ==0)
        {
          disable_interrupts();
          for(idx=0; idx < 0xFF; idx++)
            set_bkg_data(idx, 0x01, blankTile);
          enable_interrupts();
          clean =1;
        }
      }
      if ( joy & J_RIGHT)//scroll right
      {
        color(BLACK,BLACK,M_NOFILL);
        line(x,y,x,GRAPHICS_HEIGHT-1);
          if(x<GRAPHICS_WIDTH-1)
              x+=1; 
        clean =0;            
      }
      if ( joy & J_LEFT)//scroll left
      {
        color(WHITE,WHITE,M_NOFILL);
          line(x,y,x,GRAPHICS_HEIGHT-1);
          if(x>0)
              x-=1;         
          clean =0;
      }
      if ( joy & J_B)//black screen
      {
          color(BLACK,BLACK,M_FILL);
          box(0,0,GRAPHICS_WIDTH-1,GRAPHICS_HEIGHT-1,M_FILL);
          clean =0;
      }      
      wait_vbl_done();
  }
  waitpad(J_START);  // other keys are J_A, J_UP, J_SELECT, etc.
  
}