Hoshi Saga is a simple game of discovery. One part
point-and-click and one part puzzle game, the objective in each of
the game's 36 stages is to find the star. How you go about doing
that is different for every stage. The task is up to you to figure
out how.
There are 25 stages to explore freely as you wish, with another 11
stages that must be unlocked by completing rows and columns of
stages that appear on the stage select menu. The menu also shows
the relative difficulty for each stage represented by a number of
highlighted stars (out of 5).

http://ece4co.vis.ne.jp/sw/2007/05/post_16.html