Original HowCurio book club example, free to use/adapt. Read before and after source files in that order. Friday becomes Saturday; 18:30 becomes 17:00; Bring: a pencil is added. Room: upstairs, Bring: one question and Snacks: apples remain. Adjacent changed lines may form one difference block, so a block count is not a changed-field count. Native WinMerge 2.16.58.2 generated the comparison HTML with both sides read-only, without loading/saving registry preferences. Both original input hashes remained unchanged. GUI merging and saving edits were not tested.