Thank you.Let me put it this way:
Icon recognition by reading the rule book.
Brown = brown tile.
Square icon = one of red / blue / green / yellow tile.
Circle icon = one of red / blue / green / yellow dice icon.
It is written in the rule book and the summary as follows.
Brown -> square icon
Square icon -> circle icon
When I got interested in drawing the next card.
"Two arbitrary square icons -> (white arrow) two arbitrary square icons"
I had one brown tile and one red tile.
Since brown tiles are not rectangular icons, they do not satisfy the conditions.
For example, if a player discards the brown tile and turns it into one blue tile, it becomes two arbitrary square icons and satisfies the condition?
Or does the player satisfy the condition when the player has one brown tile and one red tile?
Everytime when you need a circle icon (dice), you can also use a tile of the same color instead.
Everytime you need a square icon (tile), you can also use a brown tile instead.
So yes, you can use a brown tile for every square or circle icon.