Board Game Arena

The guide says Black-Outlined circles are dangerous. I don't see any blank outlined circles on BGA. All circles look the same. If I pull up a separate pdf of the rules, I see those black outlined circles. Is this a bug or do I have some setting turned off?

There are a number of different maps you can play on BGA. The one you played doesn't have any of the black outlined circles. Most of the other maps have them (as well as other features unique to each map).