Complex sentence: Fish compared his design process to playing with Lego blocks, and for the more involved levels, he used graph paper to first visualize the 2D views since his software work built the levels in 3D.
Split into simpler sentences: Fish compared his design process to playing with Lego blocks. For the more involved levels, Fish used graph paper to first visualize the 2D views since his software work built the levels in 3D.