Expand/collapse button -> Change to make it look like a toggle

Our current design for the expand/collapse button looks like this:

The button looks the same in both states.

We should explore options that make the button look more like a toggle.

@cperessini suggested leaving it in an active state, with the darker color and inner shadow

Expand	Collapse
white background	box-shadow: inset 0 0 2px rgba(0, 0, 0, 0.2)