How does a Crystal know what object to become?

As experienced Triple Town players already know, the Crystal  is a wildcard object that will complete any match needing only one more piece. For example, if you have two Grasses next to each other, you would ordinarily have to place a third Grass next to them to complete the match and combine your Grasses into a Bush. Alternatively, you could place a Crystal next to the two Grasses; the Crystal will become a third Grass and thus complete the match, combining with the other Grasses to create the Bush. (The game is also smart enough to combine the resulting Bush into a Tree, if it happens to be adjacent to two other Bushes.)

A Crystal placed where it does not complete a match becomes a Rock. 

More interesting situations arise if a Crystal is placed in a square such that it could complete a match for more than one set of objects. For example, if there is an empty space between two Grasses and two Churches and we put a Crystal there, will the Crystal match with the Grasses or with the Churches? In these cases, the final structure worth the most points will take precedence, so the Crystal will match with the Churches to create a Cathedral because a Cathedral is worth more points than a Bush. However, as of the time this article was created there are several cases in which structures are worth the same number of points:

• Church, Super Hut, and Mountain are all worth 1000 points.
• Cathedral and Mansion are both worth 5000 points.
• Super Mansion and a Small Chest formed from 3 Cathedrals are both worth 10000 points. In some versions of the game, a Cathedral made from more than 3 churches is also worth 10000 points.

The rules on these particular situations are not consistent across game versions. However, if you find yourself in such an ambiguous situation, you can drag the Crystal over a spot before you place it, then look at which objects are bouncing (indicating which match will be made) before placing the Crystal.