Separate the board into solving passes
Pass one is for adjacent and separated matches: 00_, _11, 0_0, and 1_1 all force the open cell. Pass two is for counts, especially lines that already contain five or six copies of one value. Pass three compares nearly completed lines with finished ones. Move horizontally through each pass, then repeat vertically.
You may visually divide a long line into smaller groups to keep your place, but the rules always apply to the full row or column. A group boundary does not reset a run or create a separate balance target.
Combine the six-value quota with spacing
When a line reaches six zeros, every empty cell is one; when it reaches six ones, the blanks are zero. Before the quota is reached, list the cells that could accept the next scarce value without making a triple. If only one position remains legal, that position is forced even though several blanks are still open.
This combined check is especially effective on a 12x12 board because a line can look unfinished while already having very few valid arrangements. Confirm each placement against its crossing line before continuing.
Use line comparison without guessing
Sort your attention toward rows or columns with the same visible skeleton. If an unfinished row could become identical to a completed row under one arrangement, that arrangement is forbidden. The alternative must still pass the six-and-six count and no-three rule, so check all three conditions together.
If two options remain valid, do not commit to either one. Continue elsewhere or ask for a logical Hint. A delayed cell often resolves naturally after one of its crossing lines receives new information.
Print the large grid and keep it readable
Use the Print control after choosing a difficulty. The print layout scales the untouched 12x12 clue grid for paper and adds player fields and a rule summary. It is a clean restart rather than a picture of your partially solved browser board.
For paper solving, place a small mark at the edge of any line that already has six of one value. Work in pencil when comparing candidate endings, then darken only the confirmed digit. Finish with a deliberate audit of all twelve rows and all twelve columns instead of trusting the last placement alone.
Large-grid progress comes from disciplined passes: patterns first, six-of-each counts second, close-line comparison third, then a complete rescan. The same 12x12 strategy works in the browser and on the printable sheet.