var pic=["0px 0px","-100px 0px","-200px 0px","-300px 0px", "0px -100px","-100px -100px","-200px -100px","-300px -100px", "0px -200px","-100px -200px","-200px -200px","-300px -200px", "0px -300px","-100px -300px","-300px -300px"];

cell.style.backgroundPosition = pic[n-1];

How do i make the last cell empty

123 4 56178 12 13 14 15 Shuffle 123 4 56178 12 13 14 15 Shuffle