The sun circles the island, one step each round. Your trees earn light while it reaches them: 1 for small, 2 for medium, 3 for large.
Grove: a lit tree next to another of your trees earns 1 more. Spread your seeds.
Trees cast shadows away from the sun, as many spaces long as they are tall. Only a tree at least as tall can shade another. "Next sun" shows next round's shadows.
Tap a glowing tree, then grow it or tap a dotted space to drop a seed. Seeds land up to as many spaces away as the tree is tall.
Costs: a seed 1, then growing 1, 2 and 3. Each new tree costs 1 more for every 2 of that size you already have, so the button always shows the price. Each space acts once per turn, and Undo works until you end the turn.
Soil: the leaf marks on each space show its soil, 4 in the middle down to 1 at the edge. Soil only matters when you harvest: richer soil pays more. So grow your big trees towards the middle.
Harvest: a large tree can be cashed in for 4. It releases a burst of light that counts as collected: 10 in the middle, 8, 6, and 4 at the edge. It's always worth it on the last round.
Rocks block planting. Water gives the trees next to it +1, even in shade. The old pine can't be cut.
Brambles creep one space a round, away from the sun. Clear one within a tree's reach for 2 light.
Frost: a tree with no sun for a round wilts one size, unless it is next to water. Clouds drift and block the sun.
Duel: players take turns each round, and the first move passes between you. Your shadows fall on both players' trees. Most light at the end wins.
Forest of four: classic rules. Everyone places two small trees on the edge, then the sun goes round three times. There's no light in the first round. Harvesting a large tree scores points for its soil: the middle scores most (22, then 19, 17 and 14 at the edge), and each harvest on the same soil scores 1 less than the last, whoever makes it, but never below a minimum. Best score wins: your harvest points, plus 1 point per 3 light left.