My submission, uploaded just in time (phew!)
Arcology is a city-building game, focused on the problem of ever-rising population levels, and the need to live sustainably. By 2030 Arcologies could be financially feasible, though it's still going to be a challenge to manage them. Can you create a sustainable Arcology?
The main twists to the genre for this game are:
Population: Rises constantly, whether you want it to or not. That's how the world works. As the Governor of this city it's up to you to provide homes and food for people. Most city-building games only increase population as the player creates new houses, allowing players to freeze population levels at will. If only life was so simple!
Sustainability: The purpose of an Arcology is to be self-sustaining. If your Sustainability level reaches zero, the Arcology project has failed, and it's game over.
Connect 4: More or less The vast majority of buildings provide bonuses when built alongside specific other buildings, and you build vertically as well as horizontally. There's a whole variety of different combinations, multiple play styles to focus on, so should lead to a lot of replayability. I'm pretty sure it's impossible to construct every possible building in one play through.