R^n is Euclidean and so epsilon-delta defns work just fine. I am talking about topologies like cofinite topology or cocountable topology where the picture doesn

R^n is Euclidean and so epsilon-delta defns work just fine. I am talking about topologies like cofinite topology or cocountable topology where the picture doesn't look like a grid to which you can apply distance related notions of epsilon- room here and delta-long there.