Tents never touch, not even at a corner, so every square around a tent is grass. Mark them as soon as a tent goes in.
This is one of the Tents techniques. Each page shows its technique on the same 10×10 from the game, Hard level 3.
The rule
- Place a tent.
- Mark every open square around it as grass: beside it, above and below, and at its four corners.
In a real puzzle
On the 10×10, it’s first needed at step 19. The two open squares at the lower corners of the tent in row 6, column 9 are grass.
How often you’ll need it
On 20 of the 50 Easy levels, 44 Medium and 49 Hard: 0.6 times per Easy level on average, 2.5 on Medium and 6.1 on Hard. It’s 1 of the 22 moves on the 10×10 here.