I made up Lego Geometry to get my nephew excited about area and perimeter. Kids can create big areas by putting legos side by side, or find the area of single bricks. Tell kids not to stress if bricks don't fit perfectly on the grid paper. They can round up. Have them color the area of each of their legos on their grid paper. (Note: For younger kids, you can have them count the lego studs / dots on top to find area and perimeter).