Note: a paper version is described here (.pdf) and uses this spreadsheet to run the game live (.xls)
There is a World, a virgin landscape presided over by a female, that is waiting to be populated by plants and animals. Two male Gods will compete for this World's favor, by designing creatures and fauna that they believe will prosper in the landscape and in competition with their rival's creations. There is perpetual battle for territory and resources until one God has no specimens left on the field. But success depends on more than dominance - your creations must appeal to the female World.
When a God designs a new species, by selecting from available resources, the visual effect is of writing a “love letter” to the female World. These love letters are like genetic instructions and as they flutter down to the surface, they morph, and the new creature begins to take shape.
The design of these species has two objectives: