Energy and Laplacian on the Sierpinski gasket

This is an expository paper which includes several topics related to the Dirichlet form analysis on the Sierpinski gasket. We discuss the analog of the classical Laplacian; approximation by harmonic functions that gives a notion of a gradient; directional energies and an equipartition of energy; analysis with respect to the energy measure; harmonic coordinates; and non self-similar Dirichlet forms on the Sierpinski gasket, one of which is defined by the Apollonian packing.