Approximately 3am, I was wide awake due to heartburn and got up to go upstairs to get some meds. As I faced the stairs, a bright spotlight turned on behind me. The blinds were all closed and there are no lights or lamps that would have been bright enough or have been at that angle. I turned to see if maybe the curtains weren't shut completely, and before I turn fully to the window, there is a square of light. Kind of greenish blue. It is existing about 1ft above the ground and 1ft *IN FRONT OF* the nearest object. As soon as I see it, it closes/dims and the room is back to its normal darkness. The only explanation I have is it could perhaps be some bizarre chance of reflecting light from outside, even though the angle and position did not seem likely, but I CANNOT explain how the square was not against a surface. There was no flat surface behind it, so it shouldn't have been a flat square. I took pictures of the room and area afterward but for my mother's privacy, I'm not posting exact location or photos because I was living with her at the time. (But it'd really just be pics of a Midwestern mom's house so..) I always look for rational explanations and have debunked a few of my own personal experiences previously, but this one got me stumped.