OK so new question. I like to do the easy work first to get inspired. I don't wish to get in detail of my game. But I will build a city in Sketch-Up. Now I also need to design a ship like plane. Do I also build that but in a separate Sketch Up Pro file? And it would be nice if people posted some good FREE 3D game engines with good physics. Later on I will upgrade to Unity if I make the app but Unity Indie with iPhone Basic is $600! Thanks Also; when building in Sketch Up; do I build size by how it looks or by the real life measures? One more thing; can I use things from the Google Warehouse thing?