 but have no effect, for example when ordering a city to produce something it already produced before. The other way round, an action can be <i>not</i> ok but have an effect, although these are rare cases which only happen in the field of unit movement. The "effect" then is a gain of information. For example, when a move is impossible due to a ZoC of a non-adjacent unit that was formerly unknown, which causes the revealing of that unit.
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Another property named <i>UnitRemoved</i> tells whether the u