In CODEX Naturalis, you must continue the work of the illuminating monk Tybor Kwelein, putting together the pages of a manuscript that lists the living species in primary forests. Can you assemble them together in the best order possible? And are you ready to sacrifice a species to develop your manuscript?

In the game, each player begins with a single card on the table, a card that shows some combination of the four possible resources in the middle of the card, in the corners of the card, or both. Players also have two resource cards and one prestige card in hand, while two of each type of card are face up on the table.

On a turn, you play a card from your hand on top of one or more exploration zones that are on cards you already have in play. An "exploration zone" is a fenced-off corner of the card; your starting card has four such zones, one in all corners, while resource and prestige cards have only three.

Resource cards have no cost for playing, and they often depict resource symbols in their exploration zones.
Prestige cards deliver points when played, however they often have a resource requirement, e.g., three leaves or two wheat/one water/one stone, and you must have those resources visible in your manuscript at the time you play the prestige card. You earn points from this card immediately, with some cards having a fixed value and others a variable one depending on how many of a certain symbol are showing or how many exploration zones you covered this turn.
If you want, you can play a card from your hand face down; such a card has four exploration zones and one ressource, but offers no points. After you play, draw a face-up card or the top card of either deck to replace your hand.

When a player hits 20 points, you complete the round, then each player takes one additional turn. Players then count points based on how well they matched two public objective cards and one secret objective card, where the player with the most points wins.