Abstract: This specification describes technologies relating to the modification of pre-existing light fixtures such that the fixtures produce diffuse indirect lighting instead of direct lighting. Implementation of said technology comprises: a modular apparatus that attaches to pre-existing light fixtures to convert direct lighting into diffuse indirect lighting, and a method by which said apparatus is used for said purpose. Said technology enhances the aesthetics of an artificially illuminated environment and increases the comfort of users in said environment. Compared to alternative implementations comprising light fixture replacement, the technology specified herein presents reduced time, money, and skill barriers for users, is highly modular for simple user customization, and can be cleanly installed, adjusted, and removed without damage to the pre-existing light fixture, the attachment surface, or the apparatus.