The object is to trace a path over all the squares from Start to Goal. However, some squares will need to be crossed over multiple times.
There are 60 free 4x3 levels and 60 4x5 levels. I did the last 10 of each. The larger grids cost money. From the list below, I would say that Pathle is the one that is most similar. However, in Pathle, you must figure out the starting and ending points.
Some other good topology games:
Lines Numeric Fun
Colors the Addictive Game