Editing SimEarth (section)

== Gameplay ==
In ''SimEarth'', the player can vary a planet's [[atmosphere]], [[temperature]], [[landmass]]es, etc., then place various forms of [[life]] on the planet and watch them [[evolution|evolve]]. In the “Random Planet” game setting, the game is a [[software toy]], without any required goals. The big (and difficult) challenge is to evolve [[Sentience|sentient]] life and an advanced [[civilization]], culminating in that species leaving the planet in an exodus. The development stages of the planet can be restored and repeated, until the planet "dies" ten billion years after its creation, the estimated time when the [[Sun]] will become a [[red giant]] and kill off all of the planet's [[life]].

There are also eight scenarios that do have goals, the first three (Aquarium, [[Cambrian]] Earth, and [[1990]] Earth) involving managing the evolution and development of Earth in different stages, the next four (Mars, Venus, Ice Planet, and Dune) involving [[terraforming]] other planets to support life, and the final scenario (Earth 2XXX) involving rescuing life and civilization on a future Earth from [[self-replicating machine|self-replicating robots]] and [[nuclear warfare]] and giving the player the option of causing a [[great flood]] to help achieve this goal. In addition, there is another game mode besides Random Planet and Scenario mode, called Daisy World, where the only [[biome]] on the planet is daisies, which change their color relative to the temperature.

The game models the [[Gaia hypothesis]] of [[James Lovelock]] (who assisted with the design and wrote an introduction to the manual), and one of the options available to the player is the simplified "[[Daisyworld]]" model.<ref>{{cite magazine|url=http://www.newyorker.com/magazine/2006/11/06/game-master|title=Game Master|last=Seabrook|first=John|date=6 November 2006|magazine=[[The New Yorker]]|publisher=[[Condé Nast]]|access-date=29 July 2014|archive-url=https://web.archive.org/web/20140722213750/http://www.newyorker.com/magazine/2006/11/06/game-master|archive-date=22 July 2014}}</ref>

[[File:SimEarth IBM PC.png|thumb|225px|left|''SimEarth'' screenshot, [[IBM PC]] version. In this simulated planet, [[radiates]] have developed [[sapience]] and are beginning to form [[civilization]]s.]]

The player's control of the planet in the game is quite comprehensive; display panels allow the player to regulate everything from atmospheric gases, with percentages to three decimal places, to the rate of [[continental drift]], to the rate of reproduction and mutation of lifeforms. In addition, the player is given options to place equipment or items that interfere with the planet's development, such as oxygen generators, which increase the amount of oxygen in the atmosphere, and the [[Monolith (Space Odyssey)|monolith]], a take on the one found in ''[[2001: A Space Odyssey (film)|2001: A Space Odyssey]]'', which aids in increasing the intelligence of a lifeform through extraterrestrial influence.

The list of disasters ranges from natural occurrences, such as [[hurricane]]s and [[Wildfire|wildfires]], to population-dependent disasters, such as diseases and [[pollution]]. Effects on the planet may be minor or major depending on the current conditions. Volcanic [[Volcanic eruption|eruptions]], for example, increase the amount of dust in the atmosphere, lowering global temperature; [[earthquake]]s in a body of water may produce [[tsunami]]s; and the shortage of nuclear fuel for a nuclear power-dependent civilization may potentially trigger nuclear war and [[nuclear winter]].

[[Global warming]] can cause the planet's [[ice cap]]s to melt and sea levels to rise, but if a planet gets very hot, the oceans boil away until there are none left, only land. A planet without any water can have oceans form if hit by an "ice meteor" (a [[comet]]). Many things have to be kept within a certain balanced range for a planet to be able to support multicellular animal life; outside this range, only single-celled lifeforms, plants, robots, and lifeforms that have been civilized can survive. This excludes most lifeforms in this game since most are multicellular animals that are not civilized.

All player-triggered actions have a cost specified in "energy units" or "omega (Ω) units"; for example, 50 energy units are required to lay down a single terrain square, while 500 units are required to lay down a terraforming device. The energy budget is determined by the level of development of the planet, and the chosen difficulty level; on the lowest difficulty level, the energy budget is unlimited.

Gameplay itself can be somewhat mystifying; species may thrive or die out for no apparent reason. [[Mass extinction]]s, however, are often followed by periods of renewed evolutionary diversification, allowing the player to experiment with new sets of species and ecosystems.

===Taxa===
<!-- Deleted image removed: [[File:Simearth.JPG|thumb|225px|right|''SimEarth'', [[Super Nintendo Entertainment System|Super NES]] version. When civilizations begin to [[Industrialisation|industrialize]], [[pollution]] becomes a major concern.|{{deletable image-caption|1=Friday, 17 April 2009}}]] -->

A feature of the game is that all [[taxon|taxa]] of multicellular animals are on an equal footing, and thus it is possible to evolve, for example, sapient [[mollusc]]s.<ref>SimEarth User Manual, p. 143</ref> The two single-celled lifeform taxa, [[prokaryote]]s and [[eukaryote]]s (or [[bacteria]] and [[amoeba]]s, in the SNES version) are treated specially. Some examples of animal taxa include [[Radiata|radiates]] and [[cetaceans]] as well as more known organisms such as [[fish|fishes]] and [[birds]]. As an [[Easter egg (virtual)|Easter egg]], there is also [[self-replicating machine|machine life]], which can appear if a city of the highest technology level ([[Nanotechnology|Nanotech Age]]) is destroyed by a nuclear explosion. Machine life can thrive in any biome or environmental conditions, generally out-competing any other lifeforms present, and can itself eventually evolve intelligence and build cities. Additionally, there are Carniferns, which are mutated, [[carnivorous plant]]s, which can occur only naturally. Having an abundance of insects allows for these life-forms to develop. Carniferns are able to develop [[intelligence]] just as animals can. In addition to the familiar types, the long-extinct "[[Trilobozoa|trichordates]]" are included. The game states that "We [the game's developers] felt sorry for them, and are giving them a chance for survival in ''SimEarth''." [[Dinosaur]]s are another included taxon.

===Civilization===
Once an organism on the SimEarth planet becomes sentient and develops civilization, it will gradually go through different stages of development with each successive stage being more technologically advanced than the last.

* [[Stone Age]], characterized by the use of stone tools and [[paleolithic]] lifestyles.
* [[Bronze Age]], characterized by the use of bronze tools, the invention of farming, the development of writing, and urbanization.
* [[Iron Age]], characterized by the use of iron tools and is slightly more advanced than the Bronze Age.
* [[Industrial Age]], characterized by rapid industrialization and improving living standards. This stage is where resources are being rapidly consumed. Once this stage is achieved, energy requirements are high and [[global warming]] starts to threaten the planet's habitability.
* [[Atomic Age]], characterized by the use of nuclear energy.
* [[Information Age]], associated with the mass use of [[telecommunications]] technologies and computers.
* [[Nanotechnology|Nanotech Age]], the most challenging stage to reach due to depleting resources and the growing threat of global warming. It is associated with the use of nanotechnology and interplanetary [[Spaceflight|space travel]].

It is only possible for one species to reach sentience at a time on the planet. If the current sentient species becomes extinct, another species can achieve sentience. Once the sentient species reaches advanced Nanotech Age, they will begin the Exodus and launch all of their population into space. This entirely removes that species from the world, allowing other species to reach sentience.