This was what I came up with in 4 hours. All code was created from scratch (except the odd copy-paste of small blocks from other files).
The idea was that the user starts with a reactor, which generates energy, and a substation, which distributes energy, and then builds up a settlement with various types of building. The buildings require energy to build (not implemented yet) and run, and all building types can be upgraded.
When buildings are fully powered they are brighter, and when they are lacking power they get darker.
It is also possible to disable buildings that would normally draw power. This can be seen when buildings stop pulsing.
I didn't have time to implement a lot of elements of the game, because I spent at least half an hour getting to grips with the V2 graphics of the latest public build of Corona SDK (I needed the latest public for display.newPolygon). In particular, when an empty space is clicked a random building type is created, rather than having a build menu, and when a building is clicked it is randomly upgraded, destroyed or disabled, rather than having an options menu.
There is no audio.
Video at http://youtu.be/H_w__HFaVyE