You were measuring how much SURFACE a den covers by counting unit squares — that is called AREA! The big secret: a den's area is just the NUMBER of squares it fills, so ANY shape with the same number of squares has the SAME area. When you built neat blocks you found a shortcut: 3 rows × 4 columns = 12 squares. The area of a rectangle = length × width — which is exactly MULTIPLICATION (the same arrays you've seen before)! For twisty dens you counted squares in chunks and added them — that's decomposing area. Builders, carpet layers, gardeners and game-map designers use AREA every day!