How do I light/shade a cube so that the color is "flat" on each side?

I’m trying to light a model made of cubes so that the color is “flat” on each face, with no shading gradients. I would like the cubes to be affected by light (lighter or darker depending on which direction the faces are facing), but I want the color of each face to be totally solid. The default view in Blender shows exactly what I’m trying to achieve:

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For example, take the blue cubes in the image above. All of the sides facing in any given direction have the exact same color: a single flat shade of blue.

Compare that with what I’m seeing in Unity:

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The shadows are much “softer” and there are gradients on the cube faces. Is it possible to achieve the look the shading look in the first Blender image with Unity? What is that type of shading called? (Sorry if it’s a simple question, I come from a 2D programming background and I’m relatively new to 3D.)

Split the faces in Blender so the vertices have separate normals for each side, or set the normals in Unity when importing to “calculate”, with a smoothing angle of less than 90°.