We were down on a wooden platform that overlooks the Cuyahoga river. At some point we saw what looked like a very bright star, however the light quickly faded away. We then began seeing an object moving in the sky, appearing to both hover and move in a kind of zig-zag pattern. As it moved around it would flash a white light; almost pulsating/flashing but without any obvious pattern. Sometimes it was a quick flash, sometimes long. Sometimes the light was very bright and other times it was dim. We observed it moving during some flashes, while it stayed perfectly still (hovering) during other flashes. It was also sometimes visible as a dark outline moving when it wasn't flashing. We also observed 4 planes flying by over the course of the 30-40 minutes we observed the unidentified craft, the planes were very obviously quite a bit lower than this craft. We watched it for about 35 minutes and over that time it didn't move too far (distance wise), always stayed within our line of site, but was moving around with no observable pattern during the entire time. When we left the area to go home it was still in the sky, blinking/flashing and moving around strangely. No pictures or video were taken due to the fact that our phone cameras aren't that great, how far away the object was, and lights from the city nearby-we believed it wouldn't have been visible enough on phone images or video.