Start with 0 clues, then look for a 3 beside an edge with an X. A grid point is a corner where edges meet, and the loop uses zero or two edges there. Keep every line in one loop.
A 0 rules out all four edges around its square. Mark them with Xs, then recount the nearby clues and check that no line ends at a grid point.
Before: the four 0s are still open, so many inner edges look possible.
After: every edge around each 0 has an X. Recount the surrounding 2s, then use the grid points to find which remaining edges must carry the loop.
Turn each mark into another deduction
Finish a full clueIf a clue already touches the right number of lines, mark all remaining edges around it with an X.Fill the last open edgesIf a clue still needs two lines and has only two unmarked edges, both edges must be lines.Follow each line endA grid point with one line needs one more. If only one exit remains, continue the line there.Use a 3 beside an edge with an XA 3 needs three lines. If exactly one edge has an X and the other three are unmarked, draw lines on those three edges.
A correct clue is not the whole check
A line can match the nearby numbers and still leave a loose end or close a small loop. Before keeping it, check both end points and make sure every unfinished part can still join the same loop.