sequence grid = repeat(repeat(' ',100),100)
integer aX = 50, aY = 50,
        gXY, angle = 1                      -- ' '/'#';  0,1,2,3 = NESW
constant dX = {0,-1,0,1}                    -- (dY = reverse(dX))

while aX>=1 and aX<=100
  and aY>=1 and aY<=100 do
    gXY = grid[aX][aY]
    grid[aX][aY] = 67-gXY           -- ' '<=>'#', aka 32<->35
    angle = mod(angle+2*gXY+3,4)    -- +/-1, ie 0,1,2,3 -> 1,2,3,0 or 3,0,1,2
    aX += dX[angle+1]
    aY += dX[4-angle]
end while

puts(1,join(grid,"\n"))