Palisade
Draw lines along the grid edges, in such a way that the grid is
divided into connected regions, all of the size shown in the status
line. Also, each square containing a number should have that many of
its edges drawn in.
Controls
On a touch screen, a tap does what a click does, and a long press what a right-click does (more ways to right-click).
Click an edge to mark it as a division between regions (black), and again to return it to undecided (yellow). Right-click it to mark it as definitely not a division (faint gray), and again to return it to undecided. Keep the button down and drag to do the same to every edge you pass over that looked the same as the first.
With the keyboard, the arrow keys move a cursor around the board. Enter does what a click does to the edge under it, and Space what a right-click does.
The cursor moves by half a square, so it rests on the edges between
squares as well as on the squares themselves.
Hints
Hint explains the next step rather than simply making it, and it
always says why: every sentence names the fact that forces the move,
not just the move. It reasons only from the numbers, the region size and
the edges you have decided, your walls and your “no wall” marks, so it
carries on from wherever you are, as long as none of them is wrong; if
one is, it asks you to fix the highlighted mistakes first.
- A ring marks the edges the step decides, each as what it must become: a wall is the edge itself in the hint color, and an edge that can’t be a wall keeps its look with a cross on it. When one reason decides several edges at once they are all marked together, and each drops back to normal as you set it.
- An outline marks what the step reasons from, inside its squares: the clue it counts, the two clues either side of an edge, the four squares meeting at “this corner”, or the two regions a join would merge.
- Stripes mark the one region the sentence is about: “this region”, or “the same region” two edges both border.
The sentence says which way a ringed edge goes: “must be a wall” means
click the edge, and “can’t be a wall” (or “clear them”) means right-click
it to mark it as no wall.
A region, in the hint’s words, is a group of squares your own “no wall”
marks already join, so a single square counts as one too. The size it
compares against is the one in the status line.
These are the ideas the hint teaches, from the plainest up:
- A clue that is full, or that needs everything left. A clue that
already has all its walls allows no more, so its other edges are open;
a clue that can reach its number only if every remaining edge is a wall
gets them all. A 0 allows no walls at all.
- Regions are all one size. An edge whose opening would join two
regions into more squares than a region holds must be a wall. A region
still short of its size, with just one edge left to grow through, must
grow through it; when several edges are left and they all lead into the
same other region, the two must join, so none of those edges is a wall.
- A wall can’t stop in mid-air. Where a wall arrives at a corner and
only one other edge there could carry it on, that edge must be a wall.
- Two clues side by side. If the edge between two neighboring clues
were open, each clue’s walls would all have to go on its other three
sides, and whatever sides are left open lead further into the same
region. On boards with small regions that can make the shared region
bigger than a region may be, so the edge between them must be a wall.
Two 3s are the sharpest case: each keeps just one side open, so their
region would be the two squares alone, which is too small.
- Edges that share a fate. When two undecided edges of a clue both
border the same region, the clue’s square either joins that region,
and both edges are open, or is walled off from it, and both are walls.
It can’t do one of each. So if walling both would exceed the clue,
neither can be a wall; and if leaving both open would leave it short,
both must be walls.
On an Unreasonable board there comes a point where none of these settles
another edge, and the hint says that nothing further follows by deduction
instead of choosing for you. Save your position and try an edge beside a
number that has few edges left to decide, as a wall or as no wall: if it is
wrong, before long a number has too many walls or a region cannot reach its
size. The hint carries on from whatever you decide.
Palisade parameters
These parameters are available from the ‘Custom type…’ option on the ‘Type’ menu.
- Width, Height
- Size of the grid in squares. Each must be at least 1.
- Region size
- How many squares each region holds. It must divide the number of squares in the grid exactly, and be smaller than it. A size of 2 is allowed only on a grid one square wide or high. It must be at least 1.
- Difficulty
- Determine the difficulty of the generated puzzle; see what the names mean. An Easy puzzle can be finished one forced edge at a time: there is always a number, a region or a corner that settles an edge by itself. An Unreasonable one has a single solution that those steps stop short of, so somewhere you have to try an edge and see what follows. The Hint button stops where the forced edges do.
More help