Place a tent near every tree (horizontally or vertically). Tents cannot touch each other, not even diagonally, but can touch other trees.
MOUSE: Click on a square to place a tent. Click again to mark that there can't be a tent. A third click will eliminate any symbol.
KEYBOARD: Press 't' to place a tent. Press '-' to mark that there can't be a tent. Press DEL to eliminate any symbol.
