Math Brain Twisters With Answers

Rectslider ("Rectangle-Slider", "Shikaku suraida") consists of a rectangular or square grid with black cells. The task is to move the black cells vertically or horizontally, so black cells form rectangles having area greater than one cell. Two black rectangles must not be orthogonally adjacent. The numbers in the black cells indicate how many cells they have to pass through. Black cells without numbers may move any distance, but some of them stay put. The black cells cannot cross the tracks of other black cells and cannot move over other black cells.