<center>![Covalence unboxing.jpg](https://cdn.steemitimages.com/DQmP49kB7yHYFBvbyFzjZR7gzQG34AnyUqAGQfeW1KDHdj4/Covalence%20unboxing.jpg) *Inside the box*</center>
<center>*Covalence is a chemistry-themed cooperative card game where players work together to accurately build a number of secret organic molecules. One player has knowledge of a set of Secret Molecules. All other players must deduce what these secret molecules are, based upon clues given to them. Players must cooperatively construct their molecules before the clues run out!*</center> That’s what it says on the [web site](https://www.geniusgames.org/products/covalence-a-molecule-building-game), and they’re not wrong.

https://youtu.be/tXJ4TZSXtzc

When I was young, my family had a copy of the game Mastermind, where you have to guess a combination of coloured pegs through clues given by the other player. I hated it. I was no good at it, and the two people on the box looked nothing like Magnus Magnusson. While on the surface a similar mechanism, this is more fun and doesn’t claim to be related to a TV quiz show.

This and another game were freebies on the Kickstarter for [*Subatomic*](https://steemit.com/boardgames/@hockney/subatomic-an-atom-building-game) earlier this year. On first glance I didn’t think this game would work for two players, but we were pleasantly surprised...

Inside the box are atoms of hydrogen, oxygen, nitrogen and carbon, along with their cardboard representations. The molecules to be constructed with these atoms are depicted on cards that give their name, formula and molecular weight. Some of the molecules are familiar (ethanol being a personal favourite), while others are as obscure as they are unpronounceable. There are tokens to be surrendered when asking for clues or making guesses and two sets of cards for the giving of clues.

The game is laid out something like this: <center>![Covalence game start.jpg](https://cdn.steemitimages.com/DQmaPhAMPU8jNbYbgsYyJgoNZe12sdG4myViVkT9f4FLfYu/Covalence%20game%20start.jpg) *The player on the left is the ‘knower’, and on the right the ‘builder’. The '!!' token is for taking a guess, while the magnifyng glasses are to ask for clues*</center>

Each builder gets 3 or 4 molecule cards. They work through each molecule in turn. The ‘knower’ looks at the first molecule card and offers a free clue (‘knower’ is a shocking term, how about ~~dungeon~~ lab master? professor? answernic? cluerine?).
The clues are a combination of (up to 4) number cards and a structure card, or even none at all. For instance to make ethanol you require 6 hydrogen atoms, so I might put out ‘2’, ‘4’ & ‘H’ cards.
The builder knows that there are three larger atoms, and at least one of them will be carbon. From that and the clue, they might guess that the molecule is methylhydrazine: 
![Covalence bad guess.jpg](https://cdn.steemitimages.com/DQmNdwMmKCro5twdnHyEmfB1a9qXnYF6ADDWjQJ4vhNMXXc/Covalence%20bad%20guess.jpg)

Having heard the news that they’re wrong, the builder then asks for a clue. This can get complex, as you can only use the available cards to offer a clue. This requires ingenuity and an ability to know how the other builder will interpret your clues. The knower isn’t allowed to speak and it’s this confusion that makes Covalence such fun. It’s a lot like trying to start a land war in Asia:
https://youtu.be/EZSx3zNZOaU <center>*They should have included iocaine as one of the molecule cards*</center>

<center>![Covalence molecules.jpg](https://cdn.steemitimages.com/DQmTZDtKxXip2L7jznykpB6MXSENzaVM1ixZNE8QYqWU8tr/Covalence%20molecules.jpg) *Methylhydrazine is not Ethanol*</center>

If the builder can guess all the molecules without running out of guesses, then you’ve all won. For multiple players there’s more than one builder and they all guess and ask for clues at the same time. We’ve not played with more than two people yet. We’ve also not played the included extension pack which adds chlorine into the pool of elements.

https://youtu.be/zGM-wSKFBpo <center>*Luckily we only use the top three lines*</center>

Unlike *Subatomic*, this didn’t come with a ‘The Science of…’ booklet, which is a real shame, because I’ve no idea what most of the substances are, and only vaguely remember my A-level chemistry on such things as bonds and double-bonds.

Next up in this set of games, we’re building compounds, in *Ion*.

[Covalence: A Molecule Building Game](https://www.geniusgames.org/products/covalence-a-molecule-building-game)