I pulled the first lever but now I'm trapped on a floating platform, how do I get across?

You can't get across... yet.

As you may have worked out by now - the lever you pulled is a dual-purpose one.

What do the red and green colored lights on the pipes and levers mean?

So, you're gonna have to pull the lever again and go back the way you came.

The only way across is to some how find your way around to the other side and

extend that bridge and then find your way back again to extend the first bridge.

Why would you want to do this? You'll see.