Light Up

melantha I know about that stuff.

Oh, one additional thing: Whenever you have n suns on the neighbor cells of an n-field, mark all other neighbor cells of the particular field with x.

JohnSteel, for me some simple rules solve a great deal of the puzzle almost automatically:
(1) Mark the neighbor cells of 0-fields with x (shift-click)
(2) Put suns on fields n-fields that have only n free neighbors.
(3) Look for "isolated" gray fields (especially the ones that are x-ed out). There must be a sun that lights the field.

Of course harder puzzles are harder to solve and need some more thinking. They are not all solved automatically. However, it's quite similar to solving a sudoku.

Difficulty needs to be checked. I'm doing better on most of the hard puzzles than I am on most of the mediums.

But it appears that my save file for the 15x15 easy puzzles are still intact...
Wierd...it totally erased my times for the 7x7 easy puzzles...