This game would fit under the "educational" category (though the title was meant to be a bit provocative, yes). My idea is to have procedurally generated Earth-like planets with continents and islands with cities on them. The ocean(s) are constantly rising over time (as in global warming) and you have to build some extemely large-scale levees to keep them at bay and protect the planet and in particular, the cities. The more population you lose to flooding, the less material you get over time to build more dikes, and the player just has to keep going until the entire planet is eventually flooded. Old dikes slowly break down, so you can't just build a large circle and expect to be safe against the flooding forever.
So, in particular if we get 3d procedurally generated planets together, the player has to frantically check around to see what territory is flooding, and make split-second decisions about which cities/continents/vast swaths of not-so-densely populated land they're going to save to keep the levee-building coming. We can either have the player always eventually die, and just keep high scores, or task the player with keeping people alive until a spaceship is built in a particular position, and have levels built in.
If anyone would like to collaborate on this idea, let me know here or PM. I am at best a beginner at programming, but I can cover any necessary writing and music (plus the design).