Toehold: Sudoku Explained

Every other sudoku app has a hint button. You get stuck, you tap it, it fills in a square, and you have learned nothing. Toehold does the opposite. A panel sits beside your board and keeps a live inventory of the techniques that are available right now — "Hidden single ×2 · Pointing pair ×1 · X-Wing ×1" — updating on every digit and every pencil mark. It tells you what to look for. It does not tell you where. Tap a technique and it shows you the cells that make it true, and one plain sentence explaining why: "The only spots for 6 in box 2 — r1c5 and r3c5 — share column 5, so 6 leaves r4c5 and r6c5." Placing the digit is then a separate, deliberate tap. The toehold is yours; the climb is still yours too. DIFFICULTY THAT MEANS SOMETHING • Most apps grade by counting clues, which tells you nothing about how hard a puzzle is • Toehold grades by the hardest technique a puzzle actually requires • Gentle needs only singles. Steady adds locked candidates. Tricky adds pairs and triples. Tough needs X-Wing, Swordfish, or Y-Wing • Every puzzle is checked before you see it: exactly one solution, and solvable by named logic from start to finish. You will never be asked to guess ELEVEN TECHNIQUES, ALL EXPLAINED Naked and hidden singles · pointing pairs · box/line reduction · naked and hidden pairs and triples · X-Wing · Y-Wing · Swordfish. Each one names itself when it appears, so you learn the vocabulary by meeting it on your own board. BUILT FOR THE GRID • Pencil marks in a fixed 3x3 lattice, so a digit is always in the same spot • Fill all candidates in one tap, or place them yourself • Every key shows how many of that digit are left • Full undo • Optional mistake checking, off by default ON iPAD The technique panel stays open beside the board in a real two-column layout — not a stretched phone screen. PRIVATE AND OFFLINE Puzzles are generated on your device. No accounts, no ads, no analytics, no tracking, no network access of any kind. Free. Toehold is for anyone who has finished a sudoku and still could not say how they did it.