Getting 3 Stars

Getting 3 stars on each level is not needed in this game, but as a challenge to yourself you may want to try to do it. The star rating reflects how many moves you took to complete the level. Placing a spore counts as a move. So if you have to keep readjusting the positions then the moves add up. You will get 1 star for completing the level. But for 3 stars you need to complete it with a minimum of moves.

Keep your finger on it.

When dragging the active spores to the cell grid you can keep your finger on it and slide it around. If you don't let it go then it doest count as a move and won't hurt your score. As you move the piece it will show you on the grid the cells that it will affect and help you decide if its the right move or not.

Repeat the level

If you really want those 3 stars then the simplest way is to complete the level by trial and error and once done make a note of the positions of the spores.

Then simply replay the level and place the spores straight into the correct places. This will update your score to the maximum 3 stars.