2D/3D art is often defined by its medium and composition. Media used to create 2D/3D art may include anything that can make a mark on a flat surface. Each medium bri ngs its own unique qualities to a work of art; for example, oil paints can be reworked for days before drying and have unique depth. Composition of 2D/3D art is critical. This includes line, form, color, repetition and balance, in that order of importance. Line and form shape the appearance. Color brings out shapes and contributes mood and depth, among other things. The two principles of repetition and balance impart subtle moods. These elements arra nged in two dimensions can even create the illusion of three dimensions, as in trompe l'oeil paintings.