This was made with Adobe Sketch on an iPhone 5c with my fingers. The screen size is 3.5' x 2.5". I used Adobe sketch's "copy to clipboard" feature and inserting images feature to simulate a layer effect. This technique will be unnecessary in the next release as the new layers feature will be added including 20 layers.
Before using my fingers I tried to make a homemade stylus, but it didnt work out too well. I made it out of a pen, a paperclip, tin foil and some conductive plastic that came with my computer battery, but my homemade stylus wasn't very accurate. The program worked great with my fingers though.