This is without a doubt the most infuriating piece of software I have ever used, and I've used some corkers. I have a masters degree from Imperial College and am a chartered engineer, yet I have just spent the best part of two hours trying to draw two lines on a computer screen. I have spent an entire day trying to chase walls that move at random when they are resized, or resize themselves when they are moved. Add that to the fact that whenever two walls touch they jump several feet in a random direction and you can begin to see why I recommend that you do not buy this product. You may be planning an extension, but by the time you've even got the first storey planned you will need to rebuild the rest of the house as you will spend large parts of your day banging your head against its walls.