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# Chemistry Core Gameplay Redesign [illiux, approved]

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## Abstract

This document describes the current state of chemistry gameplay and proposes
several ways in which it might be improved. The ultimate end of these proposals
is to eliminate, as much as is reasonably possible, the reliance of chemistry
gameplay on explicit recipes. Additionally, they aim to counteract player
formation of rote builds that can be blindly repeated from round to round. This
document complements and builds on *Chemistry 1984*, which by contrast focuses on
the elimination of the dispenser in favor of the distribution of raw reagent
sources throughout various departments.

## Design Goals

Here are some guiding bullet points that influenced the design:

* There should be many possible routes towards the synthesis of a given product
* Chemists should be able to be *forced* to adapt in the face of raw reagent
availability variance
* Some may not be available at all
* Some may be available in different forms
* Chemists should learn general rules not lists of recipes
* There should still be reason for chemical laboratories to exist as distinct places
* Chemistry should be eminently possible to perform anywhere by anyone
* Though not with the same effectiveness of a proper lab
* Chemistry should allow for a decently high skill ceiling
* But we cannot afford to raise the floor much
* That gameplay should evoke real life chemical thinking
* Though this goal is subordinate to gameplay concerns

## Current State

### Issues

Chemist gameplay is...

#### Memorization based

Recipes lack patterns, and must simply be individually learned. This is a large
problem if we intend to enable chemists to adapt to missing reagents: our only
option would be to increase the number of recipes, probably by several times.

#### Shallow

The skill ceiling is comparatively low. Currently, good chemists are distinguished
only by:

* memorization of chemistry recipes and effects
* quick execution of recipes
* experience that informs what to produce and when

#### Short

Chemistry can be performed with extreme speed, a round's supply of medication
potentially produced in a few minutes. Simplistic attempts to slow things down
will, however, leave a bored chemist with little to do but wait.

#### Rote

Chemists are encouraged towards regurgitating fixed builds from round to round.
This is mostly because they can: there's little to disrupt their plan and what
disruption does occur disrupts them completely. They're never blown off course
and forced to navigate unfamiliar waters.

## Core Gameplay

*Solve et Coagula* is a Latin phrase with origins in Renaissance alchemy. Its
meaning, "dissolve and conjoin", captures the fundamental spirit of chemical
synthesis: a chemist breaks things apart and isolates them, then recombines them
into something new. This general pattern is the bedrock of the design.

### Dissolve

Nature does not generally make reagents available in forms convenient to the
chemist. The substance of interest tends to be conjoined to something and embedded
in a complex mixture. The chemist must first refine these raw resources to isolate
the reagent they desire.

#### The Separation of Mixtures

Space Station 14 (and 13, for that matter) possesses an uncommon feature: it already
has the concept of a mixture.

Currently, it is very easy to take these mixtures apart: the ChemMaster 4000 is
capable of separating each reagent perfectly and without cost. Simply removing
this functionality and replacing it with a variety of more limited solutions
enables much gameplay. Notably, since how one separates a mixture would depend only
on its composition, the resulting gameplay is not composed of recipes.

Mixtures are also very easy to randomize. We are already planning to do this in
the case of artifacts, but more restricted randomization could be applied to
almost everything. Many raw resources could merely be mixtures, needing nothing more
than separation to be usable for synthesis.

Real life chemists separate mixtures in many ways, but we cannot afford this on our
meager complexity budget. Our chemists will have only two fundamental methods
available to them: distillation and filtration.

##### Distillation

In distillation, a mixture is heated until a constituent substance boils. The
resulting gas is captured and cooled so that it condenses. This process
separates substances with a high boiling point from those with a low one.
Distillation is imperfect. If two substances have similar boiling points, they
are difficult to separate via distillation.

##### Filtration

Filtration simply separates solids from liquids. This can be near perfect - the
trick of the matter is to get the things you want to separate into separate phases
to begin with.

First, substances can be melted or frozen to transition them between solid and
liquid states. By either heating a mixture of two solids or cooling a mixture of
two liquids, one can get a mixture of one solid and one liquid. That resulting
mixture can be filtered to separate the two substances.

Second, solids can dissolve in liquids. This could conceivably operate through
a tag system: a reagent is configured with a solubility in a set of tagged
reagents. Solubility is also affected by temperature, with higher temperatures
encouraging more total dissolution. Two solids can be separated by mixing in a
solvent that dissolves one but not the other, then filtering the resulting mixture.

If one does not care to retain a liquid phase (and that phase is not dangerous
as a gas), one final option is to boil it away. In game mechanical terms, is
equivalent to distillation without gas capture.

#### Solids, Liquids, and Gases?

The distillation and filtration gameplay described above implies extending
solutions to support different phases of matter. Solids can be supported as an
additional attribute of a reagent in solution (along with its quantity). This
represents a (possibly suspended) powder. Gases can be given minimal support:
while they can be produced, they must either be immediately captured and cooled or
they become a cloud. The do not become part of the surrounding atmosphere.

With this in place reagents can be given boiling and melting points. Because
these are attributes of the reagent, they are easier to display than recipes are.
We can show in output from various in-game analysis tools.

### ...and Conjoin

Currently chemistry recipes look something like this:

1 potassium
1 silicon
1 nitrogen
= 3 dylovene

1 oxygen
1 sugar
1 carbon
= 3 inaprovaline

1 inaprovaline
1 dylovene
= 2 tricordrazine

1 oxygen
1 dylovene
1 carbon
= 3 ethylredoxrazine

These recipes are quite rigid. An easy first step to loosen them is to replace
some specific reactants with general tags. We might have an "acid" tag and a
"base" tag, for instance, and recipes that accept any acid instead of a specific
one. It might also be a good idea to allow a reagent to specify what product it
should make when used as a tag, as such a mechanic would allow for more varied
output mixtures.

We've also spent quite a bit of our complexity budget above in mixture
separation mechanics as well as created some new gameplay, so we can and should
simplify all reactions somewhat. Additionally, we can lean on that mixture
separation gameplay by having reactions with multiple products much more often.
Doing so has a nice side effect of reducing the total recipe count via
consolidation. We can also lean into this mixture separation gameplay by use of
catalysts, since they have to be separated from products.

Finally, we can make more use of temperature requirements. This has a number of
nice effects. It:

* interacts with boiling points, melting points, and solubility in interesting ways
* A mixture might not be able to be distilled, because an unwanted reaction
happens before the boiling point of interest
* The result of blindly heating a random mixture will be quite varied
* some substances will boil off
* various reactions will be triggered as it heats, possibly in a chain reaction
* can be used as a refinement step in the form of pyrolysis
* Generally, this should "undo" reactions and result in simpler products. See the
example below.
* can be used to gate a recipe with lab equipment
* allows for otherwise overlapping recipes at different temperatures
* For instance, a dylovene might break apart at very high temperatures

If we apply all this to the ethylredoxrazine and tricordrazine recipes above, we
might get something like:

5 silicon
1 potassium (catalyst)
heat >200C
= 5 dylovene + 1 potassium

1 sugar
1 <any acid>
= 1 inaprovaline + 1 <acid product>

1 dylovene
1 inaprovaline
= 1 ethylredoxrazine + 1 tricordrazine

Here's what some associated pyrolysis reactions might look like:

1 dylovene
heat >400C
= 1 silicon

1 inaprovaline
heat > 250C
= 1 sugar

1 sugar
heat > 350C
= 1 carbon + 1 water

Pyrolysis reactions of this form could potentially be displayed (and modeled) as
a property of a reagent rather than a freestanding recipe. This might look like a
thermal decomposition temperature and a list of thermal decomposition products.

### Analysis

Chemists also need to figure out what's inside their glassware. In real life,
this is complicated and hard, involving extreme precision and some of the most
expensive, bulkiest equipment around: mass spectrometers, X-ray crystallography
machines, NMR machines, etc.

Currently this best done in-game by putting the solution container in a
ChemMaster 4000 and taking a look at the reagents and their respective amounts.
You can also, to some extent, look at solution colors and descriptions.

This is not actually a bad situation. It's nice to have some mechanics gated on
bulky, immobile, and rare equipment so that chemistry labs have a reason to
exist. And, focusing the gating on analysis has some nice impacts. Chemistry
done without proper equipment ends up hard primarily because you can't really
see what you're doing very well, which leaves its skill ceiling largely unmoved
while greatly raising the floor. Working with raw resources becomes particularly
hard due to randomization, and players will need to take them to a proper lab.

We might optionally consider making analysis take a little bit of time, so it's
not *quite* so thoughtlessly used.

## Discarded/Rejected Reaction Mechanics

The above design for chemical reactions actually changes very little
mechanically. New mechanics are instead found in mixture separation gameplay.
The only addition to the reaction side of things is solution heat as a reaction
factor. This section of the document describes some other ideas for how reaction
mechanics could be changed - ideas excluded from the main design due to being
judged by the author as too expensive, in terms of mechanical complexity, for too
little gain in gameplay.

### Reaction Rates and Equilibrium

Chemical reactions currently happen both completely and near-instantaneously.
Many real life reactions do not function this way (and the reactions that do are
often termed "explosions"). To briefly explain some real chemistry, reactions
are always accompanied by a reverse reaction. The forward and reverse reactions
each have a different rate, which changes as the composition of the solution
does. Reactions reach equilibrium where the forward and reverse reaction rates are
equal, and this point often leaves some reactants around.

#### Non-instantaneous Reactions

Reactions happen at a rate primarily governed by whether they can overcome an
activation energy, which in very broad terms depends primarily on the strength
of the bonds that the reaction breaks. At higher temperatures, individual
molecules more often happen to have kinetic energy sufficient to exceed this
activation energy. As a result, reaction rates smoothly increase as temperature does.

Design-wise, reactions taking time to complete creates some possibilities. It:

* de-emphasizes the "quick execution of recipes" factor in chemist skill
* today takes the form of efficient use of the game interface
* good UI window positioning
* good knowledge of various shortcuts
* can create time for players to react (ha) to a dangerous or out of control reaction
* makes it more viable to have multiple reactions overlap in a temperature range
* this allows for minor unwanted side reactions
* which leads to more complicated mixtures to separate
* also makes heat sensitivity of reactions feel a bit less odd
* without this, they'd sudden happen at some very specific temperature

However, when separating mixtures takes time, and temperature requirements mean
*some* reactions take time to execute, we already get at least the first of
these without having to introduce a new reaction rate concept. The rest, I did
not consider sufficient to justify the implied game mechanical and technical complexity.

#### Chemical Equilibrium

Incomplete reactions can lead to some interesting problems in practical
synthesis. For instance, some reactions quickly taper off, because they are
heavily inhibited by the presence of their product. To drive these reactions to
completion, the product has to be continuously removed from solution. This can
be done by setting up a secondary reaction where the product is immediately
transformed (and later recovered). It also means that the product then has to be
isolated from the unreacted reagents.

It seems difficult to make this gameplay interesting more than once or twice so
long as we're bound to some form of recipe on the output end of chemistry. And,
it turns out, we can emulate most of the bits that are interesting merely by having
recipes with multiple products.