Low flying, large triangle having fun, playing with us.

A few friends and I all around age 15 were hanging out in a neighbors back yard when we noticed a bright light slowly moving in our direction. At first we blew it off as just an airplane.  But, as it got closer we noticed it hadn't been blinking nor did it make a sound (we had seen dozens of planes that night and this was not one).  When it reached us, moving maybe 10 miles an hour (jogging pace) we could see a shape but no real body to it, kind of like a shadow but you could not see through it at all but yet you couldn't see it, if that makes any sense? We noticed it seemed to be following the streets we lived on hovering just above the treetops. Being a football fan I can better measure distance in yardage, and I would say that the craft was flying no more then sixty yards above us and it had a triangle shape that was maybe fifty yards from point to point to point and each point was lit with a large bright white circle but it didn't hurt at all to look at them. The three of us walked and jumped under it yelling and waving at it as it turned down my street.  I ran to my house and woke my mother who came out to see it as it slowly drifted upwards and further down the street until it reached a certain hight, then took off faster then anything I have seen since, making crazy zig zags as it disapeared into the sky.
The strange thing about the whole thing is that none of us were frightened of this object.  Infact I had the impression it was playing with us...
Date is approximate.  PD