Const width = 10 In the tutorial the array is [1, width+1, width*2+1, 2] As I understand First index translates 1 => B1 Fourth index is 2 => C1 How does she point the center with width+1 and width*2+1? CSS if needed: .grid{ width: 200px; height: 400px; background-color: yellow; display: flex; flex-wrap: wrap; } .grid div{ height: 20px; width: 20px; background-color: red; } Thanks