Keyboard

• Space pause / resume
• 1 2 3 4 5 speed: paused / slow / med / fast / turbo
• v cycle view modes
• m toggle ambient music
• s toggle auto-rotation
• r reset world (regenerate)
• ? open this help
• Esc close help

View modes

• Elevation — topography; ice caps in white
• Temperature — surface temp with seasonal overlay
• Moisture — atmospheric water vapor
• Rivers — steepest-descent runoff accumulation
• Wind — zonal (east-west) wind component
• Biomes — Holdridge-style life zones
• Plates — tectonic plate IDs + motion arrows
• Vegetation — plant cover on land

Tools (left panel)

• Info — click a tile to inspect it
• Raise / Lower — sculpt terrain
• Flood — drop terrain below sea level
• Heat / Cool — change local temperature, melt/form ice
• Grass / Forest / Jungle — seed vegetation
• Animals — introduce fauna (requires plants)
• Monolith — black obelisk that advances evolution one stage
• Meteor — crater + global cooling event
• Volcano — local uplift + CO₂ release
• Industry — deforests + injects CO₂
• Deforest — strip vegetation, demote forest biomes

Sliders

• Radius — brush area (1–10 rings)
• Solar × — multiplier on the faint-young-sun curve (0.5–1.5)
• CO₂ forcing — ppm added every 100 Ky step (industrial emission)
• Axial tilt — 0–45°; drives season amplitude
• Seasons — enable seasonal T overlay in the temperature view

Climate physics

• Energy balance: each tile solves S(1−α) − (A′+BT) + D∇²T = 0 with true orbital insolation at the planet's obliquity, Budyko longwave, and diffusive heat transport (Newton + conjugate gradients on the geodesic mesh).
• Greenhouse: Myhre CO₂ forcing 5.35 ln(C/280) and CH₄ forcing, with the water-vapour feedback inside the longwave slope B. Outgoing longwave saturates at the Simpson–Nakajima limit: push past it and the greenhouse runs away.
• Ice–albedo: snow and sea ice appear where the annual-mean surface stays below −10°C (North's ice line); ice sheets persist until −4°C. Two stable climates exist for the same sun, so a snowball is a bifurcation, not a threshold.
• Water: column water vapour in mm, bulk evaporation limited by surface energy, Clausius–Clapeyron saturation, rain-out enhanced where the winds converge (ITCZ, storm tracks) and suppressed where they sink (30° deserts), orographic rain on windward slopes, a soil bucket whose overflow is river discharge in m³/s.
• Carbon: volcanic outgassing (0.1 GtC/yr) against Walker–Hays–Kasting silicate weathering, the thermostat that stabilizes CO₂ over millions of years; the ocean buffers the atmosphere through the Revelle factor. Organic burial makes O₂, oxidative weathering and reduced volcanic gases consume it: the Great Oxidation happens when burial outruns the sink.
• Methane: sits at source × lifetime; the lifetime is ~9 years in oxygen and ~10,000 years without it, so an anoxic world holds hundreds of ppm.
• Fossil fuels: a tenth of buried carbon becomes a recoverable reserve. An industrial civilization burns it at up to 10 GtC/yr until it runs out; the spike decays over ~100 kyr as the ocean and weathering take it back.
• Wind: prescribed 3-cell circulation — trades 0–30°, westerlies 30–60°, polar easterlies. (The next phase derives it from the temperature gradient.)
• Tectonics: plates with angular velocity ω×r; convergent boundaries uplift, divergent ones thin crust. (Next phase: crust advection and isostasy in metres.)
• Wildfires: ignition ∝ veg × heat × dryness × O₂; release CO₂, consume O₂.
• Energy budget (SimEarth's rule): every tool and every control-panel change spends your energy Ω. Easy 5000, Medium 2000, Hard 2000 at half regeneration, Unlimited for experiments. The planet gives back 1 Ω per step in deep time and 2–8 per step once civilizations pay taxes. The Monolith costs 2500 whether or not it works (one chance in three).
• Time scales: Geologic (10 My per step) until multicellular life, Evolution (500 ky) until intelligence, Civilization (10 yr) until the Industrial Revolution, Technology (1 yr) until Exodus, then back to Evolution as a wildlife reserve. Automatic; click the strip by the clock to lock one.
• Civilization panel: invest work hours in Bioenergy, Solar/Wind, Hydro/Geo, Fossil fuel and Nuclear (each source's efficiency depends on the technology level, and fossil and atomic fuel run out), then allocate the energy between Philosophy (fewer wars), Science (faster advance), Agriculture (population), Medicine (fewer plagues) and Art/Media (quality of life). Fossil investment is what burns the reserve and feeds the carbon cycle.
• Terraformers: Oxygenator, CO₂ and N₂ generators, Vaporator, Biome factory, Ice meteor — the tools for Mars. Pressure broadening, aerosol dust and water inventory are real terms in the energy balance.
• Events: Hurricane, Tidal wave, Earthquake (turns a plate's drift), Fire, Plague, Atomic test, plus natural hurricanes over warm seas, quakes on plate boundaries, wars, pollution and Exodus. Dust from eruptions and bombs veils the sun and decays over years.
• Daisyworld: Lovelock's black and white daisies (Watson & Lovelock 1983) on a planet whose sun brightens; the Report tab shows the temperature they hold against the bare-planet temperature.
• Phase portrait (press P): 2D phase plane of global T vs ice fraction with nullclines and Jacobian eigenvalues of the operating point.
• Console (press ` backtick): command line; type help.

Life stages

• Lifeless → Prokaryotes → Eukaryotes → Multicellular → Land plants → Animals → Sapients → Civilization. Each gated by O₂, age, and climate stability.
• A civilization then climbs a tech arc — Stone → Bronze → Iron → Industrial → Atomic → Information → Nanotech → Exodus. The Industrial age emits its own CO₂, the Atomic age risks nuclear war, a hostile climate collapses it, and a civilization that survives to the top departs the planet.

Achievements