Soren Johnson, a former designer at Maxis who spent 15 months working on Will Wright's Spore, took to his blog recently to outline the three lessons he learned while developing the 2008 game.
When Wright revealed Spore, he described a game in which players would have the ability to chart the course of a species' evolution from single-cell organism to planet-fairing hegemon. The ambitious scope, Johnson wrote, wound up playing a significant role in Spore's challenging development, which had to account for gameplay during each of these stages of evolution.
"Spore's biggest issues [sic.] was that the play at each stage was fairly shallow because the team was making five games at once," Johnson wrote. "(At one point, Will described each of the game's five stages as light versions of classics — cell is like Pac-Man, creature is Diablo, tribe is Populous, civilization is Civilization, and space is Masters of Orion.) However, making five different games at once is a bad idea; making one good game is usually hard enough."
Because each of the game's stages had different controls, objectives, interfaces and more, the desire to make them gel with each other "put the team in a state of perpetual compromise where every major decision had to be considered according to its effect across all five stages."
You can read Johnson's full postmortem and the other lessons that he learned at his blog.