The object of the game is to fill all of the grid with colored crops.
The Fields do not have to be rectangles. Some squares have rocks - no crops can grow. One more thing, a yellow field can never be next to another yellow field.
In the 'Original Release' there are 100 levels. The grid sizes range from 4x5 to 8x11. Of those 100, I've done 60 levels. Since I originally downloaded Fields, Kevin added another 100 free levels. He's also added a 'Time Trial' for those who like speed contests.