Natwerk Designs

Is there any free, easy to use stage lighting design software?

Stage Lighting Design Software...? Hi. Please can you recommend any FREE 'wysiwyg' (what you see is what you get) software, that will enable me to design lighting on a stage. However, it must be one that does not rely on the PC being plugged into a lighting board and real lights (its just for experimentation on screen) Thanks!! :D