Zinc Loft Tetras

Zinc Loft Tetras is a pure logic puzzle built around LITS, one of the cleanest deduction puzzles ever designed. No timer pressure, no luck, nothing to buy. Just a zinc plate cut into irregular regions and four letters that have to fit. HOW A PANEL WORKS The panel is divided into irregular regions. In every single region you shade exactly four cells, and those four cells must form one connected tetromino. Only four shapes are legal, and they are the ones that give the puzzle its name: L - three cells in a line with one turned off the end I - four cells in a straight line T - three cells in a line with one on the middle S - two pairs of cells offset by one step Rotations and mirror images count as the same letter, so a J is an L and a Z is an S. The square O shape is never legal, because four cells in a block break the second rule below. Once every region holds a piece, three conditions have to hold across the whole plate at the same time: - All the shaded cells form one single orthogonally connected group. No island left stranded on its own. - No 2x2 square anywhere is shaded in all four cells, not even when those cells come from four different regions. - No two tetrominoes carrying the same letter touch across a region border. Different letters may touch as much as they like. That last rule is what separates LITS from every other shading puzzle. Each region tints itself with its letter's colour the moment it holds a legal piece, so the constraint stays visible while you work instead of hiding until the end. THREE PANEL SIZES 8 x 8, the bench size, with around nine regions. Short enough to finish in one sitting and the best place to learn the four letters. 10 x 10, the shop size, with around thirteen regions. Long chains of shaded cells start to matter, so plan the joins before you commit. 12 x 12, the yard size, with close to twenty regions. The connectivity rule does most of the work here and same-letter contact bites often. Every panel is generated fresh on your own device and then checked by a full backtracking solver before it ever reaches the screen, so an impossible board can never appear. AT THE BENCH Tap a cell to walk it from empty, to shaded, to a dot you can use to mark cells you have ruled out, then back to empty. Check outlines everything that breaks a rule right now: filled 2x2 blocks, shaded islands cut off from the rest, and any pair of same-letter pieces that are touching. The outlines fade on their own. Hint completes one region for you and stamps its letter. Undo steps back through every tap, hint and clear, all the way to a clean plate. A clock runs while you work, and the panel announces itself the moment the last region falls into place. WHAT IS KEPT Panels completed for each size, your quickest run on each size, how many hints and checks you have called on, and ten shop badges running from your first finished panel through to clearing all three sizes and putting in a fifty-panel shift. Everything is stored on the device and survives a restart. BUILT TO STAY OUT OF THE WAY Fully offline. The app never touches the internet and requests no network permission at all. No adverts, no pop-ups and nothing to purchase. No sound whatsoever. Feedback is visual, with an optional short buzz you can switch off. No accounts, no sign-in, no tracking and no data collection. Portrait only, dark, and drawn entirely in flat industrial colour on brushed zinc grey. Suitable for all ages.