I'm looking for a pretty basic drafting type program for my macs. Way back in the day I used to have some sort of CAD program. It was pretty basic. You set the grid size and could draw lines, shapes whatever. Pretty much I want digital graph paper with the ability to draw on it. It's mainly for making some house/building designs go from my mind to something tangible. One of the 3d walk through simulators would be sweet too, but I probably wouldn't invest the time to make it actually work. Any help?