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In Solo Mode, what do I score if the AAA completes a City Plan before me?
You score the lower value. Plans work as in the normal game: whoever scores first gets the higher value and the other can still score the lower one. If a Completed Plan card comes up and the AAA's architect card says it does not score, you can still score the higher value. If you are holding a finished plan and the AAA scores it on the same turn, both of you take the higher value, so waiting is a gamble.