The line of sight does not need to be direct, light can bounce and still retain enough brightness to communicate. Which is also how 5ghz wifi works because 5ghz wifi also has trouble with going through objects like walls.
The 'light-based' network thing kinda threw me for a second...wifi IS technically light, its just a frequency (RF) at which we can't see it and that can (somewhat) penetrate walls.
Light is only the visible part of the electromagnetic spectrum.