We use C-Rods for math and play and we are HUGE Lego fans at our house. My son isn’t interested in building with Cuisenaire Rods in the same way he is interested in Lego, it’s not the same thing. But we use Cuisenaire Rods for math and design and it just hasn’t been an issue. We had lego long befoe Cuisenaire Rods. The Rods came after Lego.