BG-Mesh is a background in Powder Game and Powder Game 2, where air (or wind) is displayed in a grid that shows its movements much like BG-line. In BG-mesh, the grid color changes from blue, though green, yellow, red and finally dark brown when stretched on by weak to strong winds. BG-mesh can be used to observe glass when an air pressure difference is present. BG-mesh also shows explosion effects better than BG-line in most opinions. Unlike BG-line, BG-mesh shows regular wind effects better by not obstructing block nearly as much, and simply adding a more colourful and interesting effects.
BG-Mesh art uploads usually use fan and block to create complex shapes and patterns with the mesh "lines." Using air's left click function will create a circle type of mesh while right clicking creates square-like shapes. Cyclone on Powder Game 2 can also create a large and interesting effect with BG-mesh.