Practice
Practice sets.
Twenty-four trees with no date attached, three sets per level. They never change, so you can come back to one, and they do not touch your daily streak. Your progress in each set stays in this browser.
Easy.
Six by six. Every tree here opens with the plain steps Hint knows: two alike side by side, one empty branch between two alike, and a row that already has all its owls of one kind.
Medium.
Eight by eight. Now whole rows have to be counted, and the rule that no two rows are alike starts to do real work.
Hard.
Ten by ten. More counting across whole rows and columns before the tree fills up.