At the recent rummage sale at my mom's church, I paid a quarter for a baggie with several random little items. The one that attracted me was this little light (Like a small laser pointer size) imprinted with a bank's name on it. It toggles through three settings (four if you count "off") -- rapid flash, slow flash, and steady -- and made this cool circular pattern of blue light, when aimed at the bare bathroom wall. My bathroom is completely interior -- no windows, so when I want total darkness, that's where I go.
Further experimentation thunk up by my slightly demented brain yielded even cooler images of the light aimed down into the bowl of the toilet. That so mesmerized me that I was driven to go back and recreate the experience within the time frame of the current Eye of the Beholder challenge (original taken a tiny bit too early) so I could post it for that. Result (a bit different from the original, but essentially the same) can be found here: http://365project.org/mcsiegle/365/2017-09-09