In the next exercise, you'll practice changing the particle type and applying materials to it. The type of smoke you want in this scene is a cartoon-style, white, puffy smoke, which would be difficult to convincingly apply to tetrahedron shapes. So you will replace each particle with a Shape Facing particle, which is a flat square that has special animation controllers that allow it to always be perpendicular to a chosen camera.
tip
A material called Smoke is already in your Material Editor and consists of a radial Gradient Ramp map in the Diffuse color, the Self-Illumination, and the Opacity map slots. Because the Opacity map is white in the middle and black on the edges, the square shapes are invisible at the edges, so they appear round.