Tetromino is a logic puzzle that originated in Japan. The puzzle consists of a rectangular or square grid with symbols in some of its cells. The symbols can be triangles, diamonds, squares, or circles.

The objective of the puzzle is to divide the grid into regions, each comprising exactly four cells – known as tetrominoes – and each containing two symbols. And yes, tetrominoes are the same shapes you find in Tetris! For reference, here are the possible tetromino shapes:

These are just the basic shapes – tetrominoes can be flipped and / or mirrored, giving more possibilities.

Here’s what a simple Tetromino grid looks like:

- Each tetromino must contain exactly two different symbols.
- Tetrominoes of the same shape must all contain the same two symbols, though not necessarily in the same positions.
- Tetrominoes can be flipped, rotated or mirrored – they still count as the same shape whatever their orientation.
- When the puzzle is complete, every cell must be part of a tetromino, no cell can be left orphaned.

Here is the what the above example puzzle looks like once it’s been solved by drawing in the tetromino regions:

*Work from the edges.* Starting from the edges can be beneficial because there are fewer possibilities for tetromino placements. Once the edges are filled, it can make the inner sections easier to tackle.

*Start with known shapes.* Look for cells that already have symbols and try to form tetrominoes around them. Remember, each tetromino must have two different symbols.

*Rotation and mirroring.* Tetrominoes can be rotated or mirrored. This means that the same shape can appear in different orientations throughout the grid.

*Avoid isolating symbols.* As you form tetrominoes, ensure that you don't isolate any symbols. Every symbol should be part of a tetromino.

*Try using colour*. Some people find that colouring in the symbols can help them solve the puzzle more easily. That’s because some brains are wired to see colour differentials more prominently than shape differentials. Some people consider this cheating. We believe it’s a personal choice, so all of our Tetromino puzzles use unfilled symbols so that you have the option of colouring them.

*Check for consistency*. As you progress, regularly check to ensure that tetrominoes of the same shape have the same symbols. Adjust as necessary.

*Use deduction.* If you're stuck, try to deduce where symbols might go based on the remaining empty cells and the requirement for each tetromino to have two different symbols.

*Use elimination.* If you're unsure about a particular placement, consider all possible tetromino shapes that could fit in that space. By eliminating the ones that *don't* meet the symbol criteria, you can narrow down your options.

*Look for unique symbols.* If a particular symbol appears less frequently on the grid, focus on it. Since each tetromino must contain two different symbols, this can guide your placements.

*Avoid creating un-fillable spaces.* As you place tetrominoes, be cautious not to create spaces that can't be filled with a tetromino. If you notice such a space, backtrack and adjust your previous placements.

*Sketch out possibilities.* If you're solving on paper, lightly sketch out potential tetromino shapes before committing. This allows you to visualise placements without making permanent marks.

*Stay flexible.* Don't get too attached to a particular placement. If you find that a section isn't working out, be willing to erase or adjust your placements. Sometimes, a fresh perspective can help you see new possibilities.

*Break down larger grids.* For larger puzzles, it can be beneficial to break the grid down into smaller sections. Solve each section individually, then work to connect them together.

Like all puzzles, the more you practice, the better you'll become at spotting patterns and solving Tetromino puzzles more quickly. Practice with different difficulties. Start with simpler puzzles to get a feel for the game mechanics. As you become more confident, challenge yourself with more complex grids.

Want to try your hand at Tetromino? We have the perfect book for you! Tetromino: Volume 1 contains 100 puzzles over five levels of difficulty. We sometimes also feature this puzzle in our free Puzzle Weekly magazine – you should totally sign up for that if you haven’t already, as it puts 28 brand new puzzles in your inbox every week.