Source code in the phix programming language

constant ESC=27, UP=328, LEFT=331, RIGHT=333, DOWN=336
sequence board = tagset(15)&0, solve = board
integer pos = 16
 
procedure print_board()
    for i=1 to length(board) do
        puts(1,iff(i=pos?"   ":sprintf("%3d",{board[i]})))
        if mod(i,4)=0 then puts(1,"\n") end if
    end for
    puts(1,"\n")
end procedure
 
procedure move(integer d)
    integer new_pos = pos+{+4,+1,-1,-4}[d]
    if new_pos>=1 and new_pos<=16
    and (mod(pos,4)=mod(new_pos,4) -- same col, or row:
     or floor((pos-1)/4)=floor((new_pos-1)/4)) then
        {board[pos],board[new_pos]} = {board[new_pos],0}
        pos = new_pos
    end if
end procedure
 
for i=1 to 5 do move(rand(4)) end for
while 1 do
    print_board()
    if board=solve then exit end if
    integer c = find(wait_key(),{ESC,UP,LEFT,RIGHT,DOWN})-1
    if c=0 then exit end if
    move(c)
end while
puts(1,"solved!\n")