I've contributed quite a lot to Paul's simulator, including doing the port so it runs natively in the browser.

The photoresistor is just controlled by the slider in the side-bar. It doesn't respond to lights in the circuit. There is an "optocoupler" under "active building blocks" that does connect optically.

I've seen a few requests to add feedback that occurs outside the electrical domain - light is one, but also for mechanical movement (motors that turn generators). But, I pesonally think it's hard to know how to model all these non-electrical interactions in a way that is visually clear and effective.