Ok first of all, i am not one of thoose 12 year olds on forums asking people to make games for them.
I got this idea, its all about alot of matter(like those first gasses occuring early after big bang) spinning around a black hole, a few temporary gravity vortexes are placed to help speed up the forming of systems. This matter combines, some of it makes some kind of fusion reaction, creating stars, other stuff combines to become more heavy/advanced matter, like coal for example, then gravity works for us, creating planets and stuff. At some point the gameplay becomes more than watching a 4-8 star galaxy form, from theese beutfifully simulated 2d pixel planets, life arises! Each player(Or just the player) chooses one of theese randomly generated creatures and then they set keys for every muscle and voluntary action. The players can now, if their figure's features allow, to dig or gather plants or whatever, and somehow combine it, some matter can be combined to make other kinds of matter, (like plant sap and some kind of powder would become glue, wich could be useful for making tools) each player has the ability to cause the "fusion" reaction, causing new elements to be created from the ones they possesed. The player is also able, due to full control of all voluntary abilities possesed by the animal he/she controls to do advanced maneuvers, like pouring water into their mouths, applying sap to a stick and then attaching a rock, knapping rocks, sniffing random chemicals in attempt to cure some kind of medical condition, whatever. The game progresses, and within hours, if the figures controlled are able to(You can always choose "give up sentience" and wait for some fitting animal to appear) they can travel in space, perform weird experiments, blow each other up, melt another player's planet with plasma/tamed volcano whatever they want.
The "universe" itself would be simulated, think "Earth Editor from Dan-Ball", just with more.. rigid physics, pressure and heat and reactions occuring from it too, but the elements will be randomly generated, complete with physical intrisics(melting/freezing point etc.) and reactions with other elements. Gravity would allow planets to form, heat/pressure would allow geothermal stuff to happen. And there is this one mystical thing, the more "atom number" an element gets, the more crazy/useful it would be come, fission would cause it to split into elements with lesser "atom value" and fusion would cause more crazy elements. Magnetic force would just be some kind of force pushing stuff around, occuring on everything and is the actual bond of particles.
The biology stuff would be increddible simple, DNA would be increddibly simple, actual physical strings growing, controlling wich elements around them to fuse/split, and would be hard-coded elements, like a "spine here" or a "nerve here", "tooth here" etc. The brain would also be hardcoded elements, like "morale understanding" "fear hormone" "im dying, i'd better go release alot of drugs hormone", the "AI" would just be a loop of nerve signals activating different brain cells like "I am hungry, i go look for food, elements i can digest" or "That guy attacked me, spass all limbs untill he dosent move anymore/flee if theres lotsa fear hormones". Also every creature would either replicate through sex, or some kind of mix between mitosis and egg laying(Gather enough stuff and energy to produce egg and drop it), eggs would be cases of whatever material the body decides to make it off, inside DNA like the one of the layer would float among organic materials to ensure the egg wont use rock or poo elements or whatever and create HORRIBLE ABOMONATIONS, of course if you want, you can use your syringe and inject crazy elements in.
Posting more later.
The gameplay itself would be intuitive, before creatures come, you are little wispy entities capable of manipulating stuff weakly, and when they come, you have to invade their minds and try to crack them, like killing the "im an animal" braincells with small electric shocks, attempting not to damagde that balance cell over there. The player's view would be completely relative to the creature controlled, like even if you are standing on the "bottom"(wich dosent exists) of the planet, it would seem like your standing up and not just hanging, wich is the issue with most games with radial gravity. If you are so unlucky to choose an eyeless creature, the client will attempt to make some kind of visual imagery (or just point arrows or something) of the other senses, like hearing and taste. If the braincell is in the players brain, you can even imagine and dream! Wich just means that you can draw clientside materials on the screen, with the only elements being one of each states of matter(so if someone is bored they can just draw a penis or whatever), and when relaxed and eyes closed, your client will begin generating random imagery(Useful for AFK!) and maybe choose some kind of pre-generated scenery to explore, or maybe even something you remembered!(Blink eyes three times or something and the client will download the current scenery visible.) and if you are cool enough, you can find some kind of third eye/gate key to escape your mortal body, leaving it comatose, and explore the surrounding/haunt something.(Only maybe).
The players are able to communicate through chat, or if the creature has a voice, and theres a microphone, to communicate locally, audible! The player is also able to "zoom" at things, so you can see the whole of that astroid homing in on you, or when you need to get that cog-wheel right in your soon to be done planetary clock! The client would blur things out, and the time before image is clear is the half of the relative scale, so going to a 1m focus from 10m focus would take 5 seconds before you see everything pixel clear!