pi or radians(180) should do the trick.

You can use Vertex Snapping. You can enable it by clicking on the magnet icon or If you wan't to use it temporarily, hold down Ctrl. I would recommend setting the second option to active: You use it by moving your object in edit mode Tab:

Cycles: Method 1: Set the render engine to cycles Go into the node editor Check Use Nodes Delete the Diffuse Node X Click images for larger versions Method 2: Set the render engine to cycles Go into the materials panel Click Use Nodes Change the Surface to Emission Internal: Check...