Focusing on spending time around the edge of sleep on thinking about things -> sometimes seeing flashes of them -> eventually can do it on demand more? Now focu

Focusing on spending time around the edge of sleep on thinking about things -> sometimes seeing flashes of them -> eventually can do it on demand more? Now focusing on those -> trying to imagine more intricate details. Afraid it's hard to explain, and if I'd been fully aphantasic to start (including when nearly asleep) would not have been able to make any progress. Same type of issue as trying to explain how to move a specific muscle or unfocus your eyes