SimEarth: The Living Planet is a life simulation game. It was the second game created by Will Wright and was published by Maxis in 1990. In the game, players guide the development of a planet. English scientist James Lovelock advised on the game. His Gaia hypothesis, which explains how planets evolve, was included in the game. The game was available on several platforms, including Macintosh, Atari ST, Amiga, IBM PC, Super Nintendo Entertainment System, Sega CD, and TurboGrafx-16. Later, the game was released again on the Wii Virtual Console. In 1996, several Maxis simulation games were released again as part of the Maxis Collector Series. These versions worked better with Windows 95 and had different box art, with the word "Classics" added to the title. SimEarth was released again in 1997 under the Classics label.

Gameplay

In SimEarth, players can change a planet's atmosphere, temperature, landmasses, and other features. They can then add different types of life and watch them grow and change over time. In the "Random Planet" mode, the game has no specific goals. The main challenge is to help life on the planet develop into intelligent beings and a highly advanced society, ending with that species leaving the planet. Players can repeat the planet's development stages until it "dies" in about ten billion years, which is when the Sun is expected to become a red giant and destroy all life on the planet.

There are also eight scenarios with specific goals. The first three (Aquarium, Cambrian Earth, and 1990 Earth) focus on managing Earth's development at different times in history. The next four (Mars, Venus, Ice Planet, and Dune) involve changing other planets to support life. The final scenario (Earth 2XXX) asks players to save life and civilization on a future Earth from self-replicating robots and nuclear warfare. Players may also choose to cause a flood to help achieve this goal. Another game mode, called Daisy World, features a planet with only daisies that change color based on temperature.

The game is based on the Gaia hypothesis, an idea proposed by James Lovelock (who helped design the game and wrote the manual). Players can use a simplified version of this concept called "Daisyworld."

Players have detailed control over the planet. They can adjust atmospheric gases to three decimal places, set the speed of continental drift, and control how quickly lifeforms reproduce and change. Players can also place tools like oxygen generators, which increase oxygen levels, or a "monolith" (inspired by 2001: A Space Odyssey), which helps lifeforms become smarter through alien influence.

Disasters in the game include natural events like hurricanes and wildfires, as well as issues caused by life, such as diseases and pollution. The effects of these events depend on the planet's current conditions. For example, volcanic eruptions add dust to the air, cooling the planet, while underwater earthquakes may cause tsunamis. A shortage of nuclear fuel for a civilization that relies on nuclear power could lead to nuclear war and a nuclear winter.

Global warming can melt ice caps and raise sea levels. If a planet becomes too hot, oceans may evaporate completely, leaving only land. A planet without water might form oceans if struck by an "ice meteor" (a comet). For a planet to support complex life, many factors must stay within a balanced range. If these conditions are not met, only simple lifeforms, plants, robots, or civilized species can survive. Most lifeforms in the game are complex animals that are not civilized, so they cannot survive in extreme conditions.

All player actions have a cost measured in "energy units" or "omega (Ω) units." For example, placing one square of terrain costs 50 energy units, while placing a terraforming device costs 500 units. The energy budget depends on the planet's development level and the chosen difficulty. On the easiest setting, energy is unlimited.

The game can be confusing because species may suddenly thrive or die without clear reasons. However, after major extinctions, new lifeforms and ecosystems often appear, allowing players to experiment with different possibilities.

In the game, all types of complex animals are treated equally, meaning any species, like intelligent mollusks, can evolve into advanced lifeforms. Single-celled lifeforms (bacteria and amoebas) are handled differently. Examples of complex animals include fish, birds, and cetaceans. As an extra feature, "machine life" can appear if a city in the "Nanotech Age" is destroyed by a nuclear explosion. Machine life can survive in any environment and may eventually develop intelligence and build cities. Carniferns, which are carnivorous plants, can also appear naturally if there are many insects. These plants can become intelligent like animals. The game also includes extinct species like trichordates and dinosaurs, which were added as a way to give them a chance to survive again.

Once a species on SimEarth becomes intelligent and develops a civilization, it progresses through stages of development, each more advanced than the last:

• Stone Age: Using stone tools and living like early humans.
• Bronze Age: Using bronze tools, farming, writing, and building cities.
• Iron Age: Using iron tools, slightly more advanced than the Bronze Age.
• Industrial Age: Rapid industrial growth and improved living standards. This stage uses many resources and causes global warming.
• Atomic Age: Using nuclear energy.
• Information Age: Widespread use of computers and communication technology.
• Nanotech Age: The most difficult stage to reach because of limited resources and global warming. This stage uses nanotechnology and allows space travel.

Only one species can become intelligent at a time. If that species becomes extinct, another species may take its place. Once a species reaches the Nanotech Age, it begins an "Exodus," sending all its population into space. This removes the species from the planet, allowing other species to become intelligent.

Development

Will Wright met James Lovelock through Stewart Brand, a former editor of CoEvolution Quarterly who lived near Wright, after learning about SimEarth. Lovelock gave advice to the team working on SimEarth, especially helping with models of Earth's physical processes. Lovelock explained that models of Earth based only on simple sciences like biology or biochemistry often fail because they are too reactive to starting conditions and easily disrupted by unpredictable changes. Gaia models connect biology and geology, which Lovelock said remain stable and not easily disrupted for unknown reasons. Lovelock noted that SimEarth's simulation had some level of realism, even though he called it "just a game." He also mentioned that at the time, he had not seen or participated in any computer simulations of nature as large as SimEarth, and many professional climate models did not include clouds, oceans, or biological factors.

Reception

Computer Gaming World called SimEarth "absolutely fascinating." The reviewer wanted more visual clues similar to SimCity, but said the game was better than its earlier version because it had a bigger scope and could be played many times. It won the 1991 Software Publishers Association Excellence in Software Awards for Best Secondary Education Program and Best Simulation Program.

Entertainment Weekly gave the game an A− and wrote that "teaching children to care about the environment is important, but SimEarth: The Living Planet (FCI, for Super NES) has many complex parts, like temperature and rainfall, that might be too hard for young players. However, the game has value: even a simple task like 'growing a daisy' requires learning more than just pressing buttons."

The One gave the MS-DOS version of SimEarth an overall score of 95%. It said the game is fun whether players know what they are doing or not, and that experimenting with the simulation is "hours of fun." The One praised the game's large variety of gameplay, saying it offers "near-infinite variations to try." It also noted that the game has "tremendous educational possibilities" while remaining fun and engaging.