heh, very neat. You can also play around with the parameters and equation of the graph.

Check out my "tan" heart : 5 + (-sqrt(1-x^2-(y-abs(x))^2))tan(45((1-x^2-(y-abs(x))^2))), x is from -1 to 1, y is from -1 to 1.5, z is from 1 to 6