How would I create a Pacman enemy in 2D?

I'm not sure how I would create the scripted AI movement for a Ghost sprite. I am currently using transform.Translate every update and it looks very jerky.

How would I script smooth movement around a maze in 2D?

Whenever I try to use a Navmesh, because I have used quads for the maze, everywhere is non-walkable, so I cannot create a Navmesh Agent.

All help would be appreciated, thank you!