Does it work in a lit room?

Like any projector, it needs darkness for full effect. In a dim room the brighter nebula discs still read well; in full darkness the depth effect is dramatic.

How large an area does it cover?

It fills a standard bedroom ceiling and spills onto the upper walls. Distance and angle control the spread — further back gives wider, softer coverage.

Is it bright enough to keep me awake?

The nebula discs are ambient rather than harsh, and the rotation is slow. Most customers use it specifically to fall asleep, then let the timer end the session.