This is the Odwróć zaznaczenie icon for Windows 10. Here we go. Optimized for 32x32 px, these are the simplest icons in the line style. Downloadable formats are PNG and SVG, among others. Icons8 icon pack is unique in providing a huge number of icons designed by the same team of four designers who create the new icons every working day in the same style and with the same quality. Same cool as the Bat Face, huh.
It is a square with a circle inside it. The square has a diagonal line from the bottom-left corner to the top-right corner that splits the square and circle into two triangles with half-circles inside them. The top-left triangle is filled with dots outside of the half-circle, whereas the bottom-right triangle is only filled with dots inside the half-circle.