Thanks for all the interest. I filmed with my iPhone in front of a green bedsheet. Any colour works as long as it is even AND evenly lit (shadows change colours). I used an app called Green Screen by DoInk (pink octopus app logo) to remove the background and have an image or video show through – there are lots of green screen apps out there, but I like this one because it gives a lot of controls to adjust the colour of background to remove, and sensitivity (If I’d used blue, my torso would have been see-through, which is usually undesirable but can be useful for creative effects). After that I made edits in iMovie, but there are lots of editing programs out there: Adobe Premier, GoPro, Vegas, etc.