PowerUp the Game is a 3D, action strategy, multi-player, free, online game. The premise is that the Planet Helios is being destroyed from the side effects of burning fossil fuels for energy. The environment is damaged with CO2, pollution, extreme weather, and more.
Players work together in extreme environments to try to save the planet, learning about environmental issues and designing systems to harness renewable energy.
It's fun, it takes critical-thinking and problem solving skills, along with teamwork and is educational. There is a teacher's guide and lesson plans to help teachers use this in class. It combines science and engineering to address STEM initiatives.
It is available for Windows and Mac OS.
The only issue I see is that it may be blocked in some districts, like mine, because it is a "game."
The game was developed in cooperation with museums, energy agencies, and educators (including Education Connection in CT - one of our area resource centers.)
Check it out.