Merge Academy Issue

I sell things to make space if I have no more room on the board or in the cabinet. Just click on an item and look at the bottom of the board. It will show a trash can or points for the crystals you will get for selling it. Click on the green space with the crystal and +2 . The photo is what you get for the purple book. You get 1 for the red book. Also always keep items around the box of apples so they don't spawn. If there is a space next to them they always will. I keep mine in the upper corner