1. A method comprising: receiving input from a text editor containing lines of text of a script; identifying commands to control objects in a simulation in the lines of text in the editor; receiving an indication that the input changed a command in a particular line of text; identifying an object in the simulation affected by the changed command; applying the changed command to the identified object to update a state of the object at an increment of time in the simulation associated with the line containing the changed command; and displaying the simulation in a graphical display.