FAQ on Evolution

evolution faq

Below is the complete collection of the frequently asked questions about Evolution. As I collected them here, I grouped the questions into three topics (players & species, feedings, and test harnesses), tighten the prose of some questions and answers, and occasionally broke up a pair into several to clarify a point even more.

Changed in version 1.8: Sun Apr 10 20:50:12 EDT 2016
Deric and Joe asked about the ordering of auto-feeding for long necks

Changed in version 1.7: Sat Apr 2 17:12:36 EDT 2016
Lyn & Kaylie asked about the apparent conflict between 11 and Evolution

Changed in version 1.6: Sat Apr 2 09:27:16 EDT 2016
Jack & Luke’s questions about orderings

Changed in version 1.5: Fri Apr 1 21:59:41 EDT 2016
questions concerning the feeding cycle, ordering and fat food

Changed in version 1.4: Wed Mar 30 20:06:36 EDT 2016
a species traits are sets

Changed in version 1.3: Wed Mar 30 18:27:02 EDT 2016
fat food & ordering of auto feeding

Changed in version 1.2: Wed Mar 30 08:20:20 EDT 2016
JSON input modified

Changed in version 1.1: Tue Mar 29 21:46:31 EDT 2016
Marco and Lukas asked

Added in version 1.0.






When does a game end?


A game ends when before at the very beginning of a turn, there are too few cards left to perform the step 1 actions of a turn.


On Players and Species




Can a species come with two or even three identical trait cards?


Yes. No


May players perform all forms of card placements in step 3 or only one of them?


The "or" is inclusive.


May a player supplement several species boards with replacement cards?




May a player replace cards on several different species?




Silly What if two equally large vegetarians are still hungry?


In that case, the tie is broken by the order of species within the player. I have also modified the strategy description.


Silly What does ’largest’ mean ...?


The word ’largest’ always refers to an ordering. Find the ordering defined in this document.



On Feedings




What happens to food stored on fat-tissue traits if the trait is replaced?


It gets discarded.


What happens if a species with the fat-tissue trait has more food than its population minus food?


It stays around for the next turn.


What is the ordering of the actions chosen during steps 2 and 3?


In the actual game, the order matters before player n+1 gets to see part of the actions of player n before making a decision. The dealer applies the action in the following order: (1) "fill up" the watering hole (as specified by the rule) (2) add new species boards, (3) modify the boards, (4) grow the population, and (5) finally grow the bodies. All actions of the player n are applied before the actions of player n+1 are applied. After the actions are applied, the dealer proceeds to the feeding stage.

Note The description of step 4 of a turn in the Evolution rules appears to contradict the above. In software engineering terms, the Evolution document represents a requirements analysis while the project description in 11 — Designing a Protocol is the actual specification. The key here is that the latter splits the choice of determining the actions (the player’s task) and applying the action (the dealer’s task); furthermore, the dealer applies the actions at the beginning of step 4.—A software engineer might argue that this move of actions from steps 2 and 3 to step 4 is inappropriate, and I would agree. I did so mostly to make 11 — Designing a Protocol sufficiently rich and worth your while.


What is the ordering of the long-neck auto-feedings?


It is based on the current turn order.


What is the ordering of auto-feedings?


The dealer first increases the population of the fertile species, then feeds long-neck species, and finally moves fat food from tissue storage to regular food storage.


Does transferring fat food to normal food storage count as "eating"?




Is an auto-feeding for long neck’s a feeding?




Where do the extra food tokens go when the population gets reduced below the number of food tokens?


They vanish for good.


What happens if the dealer runs out of cards during a feeding cycle?


The feeding cycle continues but player no longer receive cards.


Is it true that a dealer must ask the player whether to move food tokens to a store (and implicitly how much food to move) even if a species with a fat tissue trait is the only option?


Yes, 8 — Selecting testable methods says so in the introduction, indeed, it says so in red. But, this doesn’t make a difference at this point, because we are using the Silly Strategy player, which will never choose not to store food on a fat trait. So my test cases cannot observe the difference, and your tests cannot fail because they, too, can’t observe the difference.


How does food get distributed when we have a chain of foraging and cooperating species?


A species with these two traits proceeds as follows. (1) It eats. (2) It exploits its foraging trait and eats a second time. (3) The first eat and the second eat “stack up” two “hand the right neighbor the right to eat” actions, which are run sequentially.


What happens if we do not run these actions sequentially but simultaneously, with a cooperation method that takes a natural number as an argument to indicate how many times to cooperate?


Then you get a different answer from the one I implemented when the watering hole runs out of food tokens.—This subtle difference is something that human dealers are almost never aware of, but it can influence the outcome of a game.


Can one player’s species attack another species of the same player?


No. (We discussed this and waffled, and Silly doesn’t do this, so this ruling does not affect your code base.)


Does the reduction of a species’s population during an attack reduce its food collection?




Can you supply a test scenario for this case?


(define (s-2satisfied (f 2))
  (species #:food f #:population f))
  #:doc "a population is reduced below food#"
  [attacker s-carnivore s-satisfied]
  [attackee s-2satisfied]
  #:cards 4cards
  #:pre 1
  #:post 0
  [attacker (s-carnivore 1) s-satisfied]
  [attackee (s-2satisfied 1)])


What happens when a carnivore attacks a species with horns?


In essence, the attack is executed before the feeding takes place. In detail: (1) The attackee’s population is reduced because of the attack. If the species goes extinct, the player receives two cards. (2) the attacker’s population is reduced because of the horns. If the species goes extinct, the player receives two cards. (3) Finally, the attacker’s species is fed (if still possible) and other auto-feedings take place (as still enabled). See my test case 20 from test fest 8 for an illustrative example.


Test case 20 from test fest 8 is more easily read as one of my test scenarios:


(define 2cards
  (take all-cards 2))
(define 2+cards
  (take (drop all-cards 2) 2))
(define 4cards
  (append 2cards 2+cards))
(define (s-horned)
  (species #:population 1 #:traits `(,horns)))
  #:doc "attacker -> attackee & commits suicide"
  [attacker s-hungry-carnivore s-satisfied]
  [attackee s-horned]
  #:cards 4cards
  #:pre 1
  #:post 1
  [attacker - (s-satisfied) (#:cards 2+cards)]
  [attackee - (#:cards 2cards)])


What happens when an attacking carnivore may acquire one additional food token but attacks a species with horns?


The attacker’s population is reduced because of the horns and thus cannot consume another token. As mentioned, the attack is executed first, then the attacker receives food as a reward.


Can an extinct species be attacked?


No, because species are removed when they go extinct. And, executing an attack must reduce the population size by 1 but not reduce it to below 0.


Does the body size play any role during attacks?


No, it does not unless explicitly mentioned.


Does scavenging react to the second eating of a carnivore that has the foraging trait?


No. This differs from the official rules. While scavenging itself is an act of eating and thus triggers foraging and cooperation as described about, it is a separate stage, resolved after an attack and its eating act are wrapped up.


In what order are the scavengers fed?


The scavengers are fed in the current player order starting from the current player.


What happens when the watering hole runs out of food while cooperation and foraging trait cards are served their extra food?


The feeding process starts as normal but stops as soon as the food runs out.


What happens when the watering hole runs out of food while scavenging trait cards are served their extra food?


The feeding process starts as normal but stops as soon as the food runs out. For the sake of consistency, species with these traits are served in the order in which they occur in the player sequence, starting with the current one.


What does it mean to feed "the scavengers, starting from the current player" below?


The dealer represents the current ordering of players in some way. When a carnivore eats, it finds this player and from there it traverses the entire "ring" of players, collecting all scavenger species. Once it has access to all scavengers, it feeds those as much as possible, respecting all other traits as needed.


What is the order of "auto-feedings" in a scenario such as this one: P owns S1 (scavenger), S2 (carnivore, cooperation), S3 () and S2 attacks?


S2, the active species, eats, which immediately triggers its cooperation trait. Hence, S3 eats. And then the dealer checks whether there are scavengers, starting from the current player going thru the current ordering of players-to-be-fed.


Does a foraging scavenger eat twice when a carnivore eats?


When a carnivore eats, a species with the scavenger trait eats, too. If this species also has the foraging trait, the feeding due to scavenging triggers the foraging action.


Can a species with a fat-tissue trait consume several tokens of food simultaneously?


Yes, it consumes as many tokens as possible at once.


Does a foraging species eat a second time when it takes the second food token from the watering hole or does it take two food tokens at once?


It eats twice, and it thus triggers cooperation twice.


Is the player removed from this turn’s feeding round if the response to a feed-next query is false?




Does a cooperating species hand food to its neighbor when it receives food from its cooperating neighbor?


Yes, this is called a cooperation chain.



On JSON Formats




Which of the OptSpecies in the definition of Situation represents the left and which one the right neighbor?


The first one (in position 3) represents the left neighbor, and the second one (in position 4) the right one.


Can a Feeding contain a species with population size 0?


No, because such a species is extinct.


Does the "bag" field really matter this time around?


You may send any legal value for the bag that you like. (And yes, this was a flaw in the specs. Architects make mistakes, too.)


Does a species with a fat-tissue trait always come with a "fat-food" field?


No, because there is a natural default.


Does the player in the result have to be a player that was given?


Of course.


Why does the revised document specify Species+?


I write specifications, make sure they are implementable and meet certain standards, and revise the specifications as I encounter problems. I forgot to finish the second step with respect to "fat-food".