The rules aren't very clear, how do I capture more light?
Right click to "capture" the yellow flame-looking things that spawn to get a yellow charge (you can have 4). The capture zone shows just for a few frames.
Then press spacebar to use that when you're next to a light post to light it up.
Then standing in the light recharges the blue bar, which keeps you alive, but stops yellow sparks from spawning at that post while it's on.
Sorry for the confusion!