Patterns that place the first segments
These patterns work on every grid, whatever its size. Scan the grid for them before you draw anything.
1. Zeros
A 0 means none of the cell's four sides belongs to the loop. All four edges are ruled out, which immediately constrains the neighbouring cells and dots. A 3 touching a 0, for instance, has its other three sides drawn.
2. Grid corners
The corner dot of the grid has only two possible segments: either the loop uses both, or neither. Hence two very useful rules:
- a 3 in a corner always has both outer sides drawn;
- a 1 in a corner has neither of its outer sides in the loop.
3. Two adjacent 3s
When two 3s share a side, draw three parallel segments: the shared side and their two opposite sides. The two edges that extend the shared side, at either end, are ruled out. This is often the best starting point in the middle of the grid.
4. Two diagonal 3s
When two 3s touch at a corner, each one has its two outer sides drawn, the ones pointing away from the shared dot. The loop then forms two corners facing each other across the contact point.
The dot rule
5. Zero or two segments, never one
Every dot carries zero or two segments. This simple rule drives most grids forward:
- a dot that already has two segments cannot take more: its other edges are ruled out;
- a dot with one segment and only one other possible exit must take it;
- a dot with only one possible exit and no segment yet cannot use it: that edge is ruled out.
On the border of the grid a dot has only three possible edges, and two in a corner, so deductions there come faster than in the middle.
6. Follow the line
As soon as a segment is placed, follow both its ends. At each dot, ask which exits are still possible. A line running past a series of numbers often extends by several segments before it meets a real choice.
Techniques for big grids
On Sundays the grid grows to 8 columns by 11 rows and more cells are left without a number. These two techniques make the difference.
7. No small loops
The solution is a single loop. If joining two nearby line ends would close a circuit while other segments exist elsewhere on the grid, that edge is forbidden. Think of it whenever two line ends get close: it is a free elimination.
8. Inside and outside
A closed loop splits the cells into two zones, inside and outside. Everything beyond the edge of the grid is outside. Crossing a segment switches zones; crossing an empty edge does not.
- A 0 is in the same zone as its four neighbours.
- A 3 has three neighbours in the other zone and only one in its own.
- Two neighbouring cells separated by a ruled-out edge are in the same zone.
Bouclo does not let you shade cells, so do this reasoning in your head on a small part of the grid. It often unlocks areas where numbers are missing.
Protecting your score
The game ends as soon as your loop matches the solution. The score out of 1000 accounts for time, mistakes and jokers. You can draw, erase, undo and cross out freely: a mistake is closing a loop that does not match the numbers.
A single mistake costs only a few points, but they add up to as much as half the performance score. A joker costs about 60 points, so keep it for a grid that is truly stuck.
To review the rules and a sample grid, read how to play Bouclo. For a change of logic, try Binero, SIWA's Takuzu.