He probably means the following rule
"The game must have step movement on a grid. Smooth transition between grid squares is allowed. Half-steps or dividing the square into smaller squares is not accepted."
You seem to have 90 degree turning but forward movement isn't adhering to a grid or on a step-basis. Have you ever played a game like Legends of Grimrock or older games like Eye of the Beholder or any Wizardry. They all have dungeons entirely based on a grid (not just the map, but the very movement itself is fixed on a grid and happens step-by-step