FEAR MY RUN ON SENTENCES THAT RESULT FROM ME EXPLAINING SOMETHING AS A STREAM OF THOUGHTS!

the idea keeps popping into my head to make a roguelike game where the alchemy system for making potions is randomly generated.

potions would be able to have a set number of effects, as well as a combination of these effects, good and bad, it then creates about 12 types of chemicals, chemicals when mixed in certain combinations and quantities make different effects, so 2 chemical A's mixed with one chemical B will make a healing potion for example, swap chemical B for chemical C and it would be an invisibility potion. chemicals (as well as every item in the game) will then be assigned a value variable, which keeps track of how useful it is, then makes the most valuable materials rare, or hard to obtain.

chemical C would be very valuable because you could combine it with chemical A, a fairly common chemical, so getting chemical C makes it easy to make an invisibility potion, which is very powerful. because of it's high value, chemical C will only appear in a few ingredients, which are in turn made valuable, and due to that, are only found rarely, or alternatively, only in hard to reach areas (inside an active volcano for example) or from hard monsters. the most valuable of chemicals would only be available by pre-treating certain ingredients to get an essence of BLANK.

many ingredients will be made using a random algorithm, and each one gets a mix of ingredients (I would need to work out a set of rules for balancing these mixes so a player would not end up with ONLY very valuable ingredients which they can't find, or so they only find low level ones)

now those ingredients being a mixed bag of chemicals allows the game to have a chance to have bad effects to the potions or good effects on poisons, like in elder scrolls, as there may be surplus chemicals in your invisibility potion that mix together to form harmful effects, decreasing the value of the potion, making those ingredients easier to find. this means low level invisibility potions might also poison the user, or make them go blind.

it is a lot like a mix between skyrim's "mix two ingredients and if they have the same effect listed then the potion will have that effect" and witcher's "combination of chemicals make an effect" mechanics, but with an added layer of complexity.

this complexity was the original goal of the idea, as I wanted to have a system that would make it nearly impossible for the player to guess the ingredients to a potion, meaning they must find written recipes listing specific ingredients, or (and this is the interesting bit) research the chemicals in books, which would add the combinations of chemicals to a list on the side of the UI needed for specific effects. they could then spec into the alchemist tree to be able to experiment with ingredients to find out what chemicals they contain, then use that knowledge (and a handy UI tool for planning and storing recipes (the alchemist's journal)) to invent your own potions.

I had always liked the alchemy in skyrim/oblivion/witcher, but thought it could take more of a central role in a game. with experimentation and proper planning and strategic brewing would be very rewarding to an alchemist.

other possible mechanics include alchemist shops which will brew potions on request if you bring them certain ingredients if you do not play an alchemist character. high level alchemists will be able to refine their ingredients into liquids that have more of certain chemicals and less of others. (perhaps ingredient C will be destroyed by high heat but D will be evaporated when boiled, and E will be destroyed when exposed to acid, to get a refined chemical D you would boil it then collect the evaporated liquid, to get chemical E you could boil it off to get rid of C and D, ingredient C could not be purely refined from this specific ingredient because by boiling it to get rid of D, you also destroy the chemical you want, but you could still partially increase its effect by adding acid to it to destroy chemical E, making it 50% less diluted)

oh and in the traditional roguelike style, you do not know what a potion will do until you use it./have it identified by an alchemist/yourself with a high enough skill/learn the recipe for it beforehand.

Man, I would totally play with a system like that. However, with complex, recipe-based setups, you run the risk of having most of your players resort to guides to find the best potions and ingredients, which removes all the fun of experimentation. It's really depressing how many people use guides for things like this, probably because to them, the alchemy isn't a puzzle, but an obstacle or necessity to reach a greater cause (see Skyrim).

I've seen some games randomize ingredients or effects of certain items, so maybe that would be a viable solution. For example, a mushroom that previously healed you might paralyze you in another run or poison you in yet another.

killin, that is why it is randomly generated each game, so guides are impossible other than for learning the basics and understanding how the system works, which is exactly what I want. the seed of this idea was re-playing skyrim once I already knew all the best combinations of ingredients, I knew how to make the best potions without bothering to spec into alchemy to learn the effects of the ingredients. then I saw witcher 2's method, where you have to combine plants and such with different alchemical compounds, but you actually require the recipe in order to make it. If I could come up with a method that meets these in the middle, so you can't use knowledge from a previous life in order to learn recipes, but you are also able to experiment, and strategically design your own potions with a system which is as much of a game in itself rather than just clicking on a couple of ingredients in a UI and pressing craft.

It should not be an obstacle, it should be a ludologically sound game mechanic

If I could, I would make an AI that mimicked a person flawlessly with speech and everything. /That/ would the penultimate game. You could literally do anything. Take over the world, make a conspiracy. Heck, you could even give an NPC all the power and watch from the sidelines. It would be epic.

But let's be more practical…

I prefer randomly generated levels more than anything, AS LONG AS THEY ARE DECENT. I don't want to just wander around a labyrinth. I would rather have puzzles and door. More like an actual area to work through than just a giant place to kil endlessly spawning enemies.