Twitter could be getting a night mode
It's that extra option which replaces as much of your screen as possible with darker colours, making it less bright when you're trying to read at night or in a place where the flow of your display might be distracting. It can also be easier on the eyes for extended reading, like in an e-book reader.
The option to switch between day and night modes is most welcome but unfortunately rarely offered by major apps. You can get the effect of it, to some degree, with a third party screen dimmer, but that can compromise the viewing experience.

