Floof Cat is having a bad day.
1) I go down this morning to make coffee. Floof Cat requests front door opened so that she can observe outside, sniff the air, and maybe go sit on the stoop. Start to open door and Floof Cat immediately starts hissing. Neighbor Cat is sitting on the stoop and decides he wants to come in! I get door closed before Neighbor Cat gets in while Floof Cat flees into the dining room. (Neighbor came by a few minutes later and retrieved her cat.)
2) I open upstairs window behind computer desk a bit so Floof Cat can sit on the sill and sniff air as compensation. Ice falls on porch roof right in front of the window, or a bird bounced off the screen. In either case “sudden object appears in front of my face!” and Floof Cat panic jumps onto the computer table and runs out of the room.
Gave her a few treats and recommended a quiet nap somewhere.