It's built in a modular way. The "world" (renderer, building state, lift behavior) is separate from the "controller" code, which determines which lift is sent to which floor when someone presses a button.
See it in action at http://simlift.meidosem.com/.
This project explores Solomon "Sol" LeWitt's wall drawings, where each piece is defined by a set of instructions that are left open to interpretation by other artists that execute the works. It randomizes the ambiguous properties of each drawing to play with the constraints of each work. You can see the code here: https://github.com/jaryncolbert/solitude