What Am I?

This object doubles as a barrier between winning and losing. It is also a place where cheers of excitement or groans of defeat are heard. This object rests on a soft, viridescent surface that is home to many. A white mesh stretches and clothes this object. This object has a solid base but does not have an actual solid form.  This object also has no actual shape, it could be considered a rectangle or a triangle depending on what angle you view it from.