I had one very similar to that on my window. We let it be. Although unlike you I cannot look at a spider and see anything but ceepy
..but it was unique enough so we tried to get a picture..I take all my pictures from my phone so it is hard to get a close up but it had a white spot on its back, smaller legs, and almost neon green by his fangs. Do you know what kind it is? We tried to look it up online to no avail.