Slitherlink: dots, counts and one loop
Most of a Slitherlink is solved by three small rules: a number counts its lines, a dot has two lines or none, and there is only one loop.
How it works
The patterns get you started. After that, nearly every move comes from three rules you already know, used again and again.
A number counts its lines. A dot has exactly two lines or none, because the loop passes through it or misses it. And the loop is one loop, so it can’t close until it has everything.
Keep going until nothing moves
Each rule unlocks the next. A cross at a dot leaves one open side, so a line goes on. A new line fills a number, so its other sides are crossed.
Sweep the board for each rule in turn. When none of them moves anything, look for a pattern or try a side both ways.
Worth memorizing
A number with all its lines crosses the rest.
A number with exactly enough open sides takes them all.
A dot has two lines or none.
Two lines: cross the rest. One line and one open side: draw it. No line and one open side: cross it.
The loop can’t close while other lines or unmet numbers are left.
Practice
0 of 3 rightThe ringed dot already has two lines. What is its last side?
The ringed dot has no line and one open side. What is that side?
A line ends at the ringed dot, and one side is still open. What is that side?