Coilu

Coilu is a cage-arithmetic logic puzzle you can play entirely offline. Fill an N×N grid so that every row and every column contains each number from 1 to N exactly once, then satisfy the outlined "cages": each cage prints an arithmetic target and an operator (+, −, ×, ÷), and the numbers you place inside it must combine to hit that target. It is a Latin square with an arithmetic twist — from the KenKen family, and deliberately not Sudoku. Every puzzle is generated on your device 📱 by a genuine engine: a Latin-square generator, a cage carver, and a backtracking solver that guarantees each puzzle has exactly one solution and rates its difficulty 📏 by how much deduction it demands. There is nothing to download and no half-baked boards — only solvable, uniquely-determined puzzles across four grid sizes (3×3 up to 6×6) and four difficulty tiers, from Easy to Expert 🏆. Tools 🛠️ that make solving feel good: • Pencil marks for candidates, with optional auto-cleanup when you place a final value • Live conflict checking that flags a repeated number 🔢 in a row or column, or a cage that misses its target 🎯, the instant ⚡ it happens • Undo, erase and reset, plus a calm, non-punitive timer • A first-run tutorial and a LEARN 📖 section with real techniques and an interactive demo cage you can tap 👆 through Track your play ▶️ in RECORDS: solved counts and best times per size and difficulty 📏, a solve-time ⏱️ visualization, and a Trophy Wall where you can attach a personal photo 📸 — taken with your camera or picked from your gallery — to each difficulty you have conquered. Every puzzle also carries a short seed code, so you can reopen an exact board later or hand one to a friend, all computed locally. Coilu keeps everything on your device 📱: no accounts, no ads interrupting a solve, and no network needed to play ▶️. If you enjoy Latin squares, KenKen-style math 🧮 cages, or simply a quiet, honest logic puzzle, Coilu gives you an endless, always-fair supply.