Teaching board Tango Level 3: 6×6 cells, 3-and-3 balance per line, no triple runs. Students should read 13 locked clues and 4 signs before filling anything — lesson one is never guess when a line is one symbol short of balance.
Coach note: teach the three global rules together — balance, no-three, and signs. × pairs dominate this board — opposite signs force alternating symbols and quickly eliminate one option per linked cell. On this board, opposite-pair propagation means students should prioritize opposite pairs early.
Phase 1 for students: place R2C3 → Sun (only one symbol still valid); R2C5 → Sun (column balance closes the line); R2C1 → Moon (row balance forces the last symbol). Phase 2: verify row and column counts after each placement — ask "does any line now have two suns (or moons) in a row?" Phase 3: finish with R6C5 → Sun and R6C6 → Moon; if a student is guessing here, they skipped a balance check.
Line balance check: Every row and column holds exactly 3 suns and 3 moons (row 1: 3 suns, 3 moons; row 2: 3 suns, 3 moons; row 3: 3 suns, 3 moons; row 4: 3 suns, 3 moons; row 5: 3 suns, 3 moons; row 6: 3 suns, 3 moons). That 3-and-3 split is the backstop when signs alone do not decide a cell.
Constraint verification: 0 equal signs require matching neighbors; 4 opposite signs require different symbols. A single broken edge means the grid fails even if row balance looks correct.
No-three rule pass: scan every row and column for three consecutive suns or moons — none appear in the completed grid. Sandwich cases (sun-moon-sun patterns around a filled pair) often force the middle cell and show up as two matching symbols sandwich this cell deductions on boards like this.
Recap for students: 13 givens + 23 deductions = full 6×6 board. Replay focusing on opposite-pair propagation reads before using hints.