Slitherine

I have noticed that when a unit is on a mountain it can spot out to two hexes. On the turn when the same unit leaves the mountain for a hill for flat hex, for that turn it can still spot out to two hexes, but only one of them is highlighted as to what it can actually see. As an example, a unit just moved off of a mountain hex and two hexes out was an observatory. While the unit could "see" the observatory, the game didn't recognize the observatory as having been seen. Therefore, two game turns later when the unit moved adjacent to the same observatory, the game gave an event indicator that I had discovered an observatory.