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Statistics Difficulty Time Great Work New Game Loading View Weekly Tournament Results Total Score Best Score Today This Week This Month All Time Tournament See All Position Improved Dropped No change Statistics Score Easy Medium Hard Expert Master Extreme Evil All-Time New Best Score New Personal Best Great Work Your Awards Track progress, level up, and keep your streak alive. Awards Earned Puzzles Completed Current Streak Best Streak Next Up Trophy Cabinet All Unlocked In Progress Repeatable Please log in to view your awards. Login/Register Award Unlocked! View Awards Settings Close Colour cell shading Tap a colour, then tap any cell to shade it. Auto pencil Dark Mode Hide Completed Numbers Puzzle Information Puzzle ID Puzzle SE Rating Hardest Technique Light Purple Light Pink Light Green Light Brown Light Yellow Light Red Light Dark Green Light Orange Light Beige Light Grey Hint Next Done Previous OK Pay attention to these cells and the highlighted areas. Since it is the only possible option, must be Row Column and that cell the highlighted cell(s) Full House means a row, column, or box has only one empty cell. The missing digit for that house must go into that last cell. A Hidden Single occurs when only one cell in a row, column, or box can take a particular digit. That cell must be set to that digit. A Naked Single is a cell where only one candidate remains after looking at its row, column, and box. That candidate must be placed there. Locked Candidates Type 1 (Pointing) happens when all candidates for a digit in a box lie in one row or column. Those candidates can be removed from the rest of that row or column outside the box. Locked Candidates Type 2 (Claiming) occurs when all candidates for a digit in a row or column are confined to a single box. That digit can be removed from other cells in that box. A Hidden Pair appears when exactly two cells in a house contain the same two candidates. Those cells must take those digits, so other candidates can be removed from them. A Hidden Triple is three digits that only appear in three cells of a house. Those cells must contain those digits, so other candidates can be removed from them. A Hidden Quadruple is four cells in a house that are the only places for four specific digits. Those cells must contain those digits, so other candidates in them can be removed. A Naked Pair means two cells in a house share the same two candidates and no others. Those digits can’t appear in any other cell in that house. A Naked Triple is three cells in a house whose candidates are limited to exactly three digits. Those digits must occupy those cells, so they can be removed from peers. A Naked Quadruple is four cells in a house that together contain exactly four candidates. Those four digits must fill those cells, so they can be removed elsewhere in the house. X-Wing is a simple fish pattern using two rows and two columns. When a digit appears in exactly two cells in each row and they align in two columns, that digit can be removed from other cells in those columns. Swordfish is a three-line fish pattern. When a digit appears in exactly three rows and three columns in a particular arrangement, you can remove that digit from other intersections. Jellyfish is a four-line fish pattern. When a digit appears in exactly four rows and four columns in a coordinated way, you can remove that digit from intersecting cells outside the pattern. Skyscraper uses two pairs of conjugate candidates in different rows or columns that share a common line. One of the pair positions must be true, so the digit can be removed from cells that see both pairs. Two-String Kite links two conjugate pairs (strong links) in a row and a column. Where those lines intersect, you can remove the shared digit from peers. Turbot Fish follows two strong links connected by a weak link. The structure means one candidate must be true, so you can remove the same digit from cells that see both ends. Empty Rectangle uses a nearly empty rectangle pattern in a box and its intersecting row/column. That shape shows that certain candidates can’t appear where they would create a contradiction. Unique Rectangle is a uniqueness technique that avoids a deadly rectangle pattern which would lead to multiple solutions. The puzzle’s uniqueness forces certain eliminations or placements. Hidden Rectangle relies on a deadly rectangle pattern that would give multiple solutions. The uniqueness requirement forces one of the candidates or cells to behave in a specific way. Avoidable Rectangle prevents a rectangle of candidates from turning into a deadly pattern. To keep the puzzle unique, at least one candidate must be eliminated or fixed. A BUG+1 pattern with exactly one extra candidate means the puzzle would have multiple solutions unless one move is made. That extra candidate must be the true value. XY-Wing involves three cells: a pivot with candidates X and Y, and two wings that share XY pairs with it. Because one wing must contain a third digit, you can remove that digit from cells that see both wings. XYZ-Wing extends XY-Wing with three digits in the pivot cell. Whichever digit the pivot takes, one of the wings must take another, so a third digit can be removed from the intersection. W-Wing links two identical bivalue cells using a strong link on one of their digits. Because one of those cells must take that digit, the other digit can be eliminated from certain peers. Sue de Coq splits a house into overlapping cell sets whose candidates form a tight combination. The arithmetic of what must fit where leads to powerful eliminations. Simple Colors colors candidates in conjugate pairs (strong links). When both colors see the same cell, one color must be wrong, so those candidates can be removed. Multi Colors looks at several coloring chains for the same digit. When different color groups interact, some colored candidates must be true and others must be false, giving eliminations. Remote Pair follows a chain of bivalue cells with the same pair of candidates. If both ends of the chain see another cell, one of the candidates can be eliminated there. X-Chain follows alternating strong and weak links for one digit. The chain proves that some candidates must be true or false, letting you remove others. XY-Chain uses a chain of bivalue cells where each link shares a candidate. If the two ends see the same cell, one digit must be true at one end, so that digit can be removed from the common peer. Nice Loop and AIC use alternating strong and weak links in chains or loops. The structure proves certain candidates must be true or false, allowing placements or eliminations. Grouped Nice Loops use groups of candidates inside strong/weak link logic. The grouping lets you make the same style of deductions at a higher level. ALS-XZ uses two Almost Locked Sets that share candidates. The way those candidates interact forces eliminations in cells that see both sets. ALS-XY-Wing links almost-locked sets through shared XY relationships. Because one end must contain a digit, you can remove that digit from intersecting peers. ALS Chain connects several Almost Locked Sets. The chain passes restrictions along, allowing eliminations or confirmations. Death Blossom uses a pivot and several petals that share candidates. The overlap forces eliminations because the shared digits cannot all remain possible. Templates use a pre-defined pattern that matches a known structure. Once the pattern is recognized, it leads to immediate eliminations or placements. Forcing Chain assumes a candidate is true and follows the logic until it forces a result or contradiction, proving something must be true or false. Forcing Net is a wider forcing approach where multiple assumptions are explored. If all paths lead to the same outcome, that outcome must be correct. Kraken Fish extends fish patterns with chains that connect candidates outside the basic grid geometry. Those chains force eliminations beyond the normal fish intersections. Brute Force is a last resort approach that tries possibilities when logic runs out. It is included for completeness, but logical hints are preferred. Full House Last Digit Hidden Single Naked Single Locked Candidates Type 1 (Pointing) Locked Candidates Type 2 (Claiming) Hidden Pair Hidden Triple Hidden Quadruple Naked Pair/Locked Pair Naked Triple/Locked Triple Naked Quadruple X-Wing Swordfish Jellyfish Larger Basic Fish Finned/Sashimi X-Wing Finned/Sashimi Swordfish Finned/Sashimi Jellyfish Larger Finned Fish (Finned) Franken Fish (Finned) Mutant Fish Siamese Fish Skyscraper 2-String Kite Turbot Fish Empty Rectangle Unique Rectangle Type 1 Unique Rectangle Type 2 Unique Rectangle Type 3 Unique Rectangle Type 4 Unique Rectangle Type 5 Unique Rectangle Type 6 Hidden Rectangle Avoidable Rectangle BUG+1 - Binary Universal Grave + 1 Unique Rectangles with missing candidates XY-Wing XYZ-Wing W-Wing Sue de Coq Simple Colors (Color Wrap/Color Trap) Multi Colors Remote Pair X-Chain XY-Chain Nice Loop/AIC Grouped Nice Loop ALS-XZ ALS-XY-Wing ALS Chain Death Blossom Templates Forcing Chain Forcing Net Kraken Fish Brute Force Grouped Discontinuous Nice Loop Puzzle Link Copy Copied Copy failed

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