Paint on one side of the paper only. Then fold it, press it flat, and open it up again — the paint prints itself onto the other half.
Choose a colour, then draw on the left half. Press Fold and press to reveal the mirror image. Open it again to add more paint. Save your picture when you like it.
Paint
Brush
Way of painting
The fold makes a line of symmetry. Everything on one side lands in exactly the same place on the other, only flipped. Many butterflies and leaves show this kind of approximate balance — paint close to the fold and you get a body, paint far from it and you get wings.