Pell the barn owl is filling the hollows of the Great Oak before winter. Swipe a treasure into its neighbour to swap them. Line up three or more of the same kind in a row or column and they are gathered.
Helpers you can make: 4 in a row makes a Hoot (it clears its whole row or column). An L or T shape makes a Nest Burst (clears the squares around it). 5 in a row makes a Moon: swap it with any treasure to gather every one of that kind. Swap two helpers together for a bigger surprise!
Goals: gather treasures, peel the moss (match on top of it), thaw the frost (frozen treasures can't move, but you can match them), clear the leaf piles (match next to them) and bring the chicks down to the bottom (a chick can always hop down: just swipe it down). Finish within your moves. Fewer moves = more stars. Moves you don't need turn into a Moonlight bonus.
Endless: score as much as you can; big scores earn extra moves. Zen: no moves, no end. Daily Hollow: a new puzzle each day, the same for everyone.
Mouse or touch: swipe a treasure, or tap one and then tap its neighbour.
Keys: arrows move the cursor, Space or Enter picks a treasure, then an arrow swaps it. Esc cancels, H shows a hint, P pauses, M mutes.
Stuck? Wait a moment and a ghost finger shows a good swap (turn Hints off in Settings). If no swap is possible, Pell stirs the hollow for you.