Summary: A tetromino puzzle is a small board plus a bank of pieces made of four squares, and you win by placing every piece so the whole board is covered with no gaps and no overlaps. This guide covers the five shapes, the rules, a complete worked example and the tips that get kids and first-time solvers to the end.
Overview
A tetromino is four squares joined edge to edge. There are five different shapes, each named after the letter it looks like: I (a straight line), L, O (a 2×2 square), S and T. If you know the falling-blocks video game, these are its pieces — its J and Z are simply the L and S flipped over, so here they count as the same shapes.
A tetromino puzzle prints a board — usually a small rectangle, sometimes a drawn shape — with the pieces you must use shown underneath. A shape can appear more than once in the bank. With only five shapes and four squares per piece, tetromino puzzles are the gentle way into shape puzzles for kids and beginners: quick to read, quick to solve, and easy to cut out and move by hand.
Tetromino Puzzle Rules
- Fill the board. Every square must be covered.
- Use all the pieces. Each piece in the bank goes on the board exactly once — if the bank shows three L pieces, all three are used.
- No overlaps, nothing off the edge. Pieces sit side by side, never on top of each other, and never over the edge of the board or into a hole.
- Grey pieces are already placed. Those starter pieces are fixed; fit the bank around them.
- Turn and flip as the puzzle allows. The instructions say whether pieces can be turned and flipped, turned only, or kept as printed. If they don’t say, pieces may be turned and flipped.
The letter printed on each piece in the bank tells you its name, so you can talk about it (“the T goes in the corner”) as you solve.
A Worked Example
Here is the puzzle above, step by step. The board is 4 squares wide and 6 tall, three grey starters are already placed, and the bank holds an I, an L and a T — 12 squares to fill.
- The bottom-right corner first. The empty square in the bottom-right corner can only be reached from above, and the squares above it bend left on the third row up. Only the L has that bend: its long side runs up the right edge and its foot turns left.
- The left edge next. The left column has five empty squares in a row. The straight I covers four of them — but if it starts at the very top, the square at the bottom is left on its own, which no piece can fill. So the I goes in the lower four squares.
- The T fills the rest. The four squares left at the top — three across and one below the middle — are exactly the T. Board full, every piece used.
Turning and Flipping
With turned and flipped, an L can face any direction and can also be flipped into a backwards L, and an S can become its mirror image. With turned only, the L and the S can still spin round but never become their mirror images; the I, the O and the T look the same flipped anyway, so they are unaffected. With kept as printed, every piece goes down exactly as the bank shows it. Turned only is the usual next step once a solver finds the easy puzzles quick.
Does a Tetromino Puzzle Have Only One Answer?
Every puzzle can be solved, and most are made with exactly one solution: while the puzzle is generated, starter pieces are added until only one way to finish remains. So if a piece fits in only one place, it belongs there — and the grey starters are a deliberate part of the puzzle, which is why harder puzzles still show a few. Some activity sheets are open challenges instead; on those, any full covering that uses every piece is a correct answer.
Tips for Solving
Place the I and the O early. The straight I can only lie flat or stand up, and the square O always looks the same, so they have the fewest choices. Find where they can go first.
Start in a corner. A corner square can only be covered in a few ways. Fill the tightest corner, then work along the edge.
Keep empty spaces in fours. Every gap you leave has to be filled by whole pieces of four squares, so a closed-off gap of 1, 2, 3, 5, 6 or 7 squares means a piece is in the wrong place. A gap of 4 or 8 can still be the wrong shape, so check it against the pieces you have left.
Let the starters split the board. The grey pieces cut the board into smaller spaces. Finish the smallest space first — it often fits only one shape.
For young solvers, use real pieces. Cut out the bank and let children slide and turn the pieces on the printed board. It turns the rules into something they can feel, and it quietly teaches area, turning and mirror images.
Puzzles on Shaped Boards
A board does not have to be a rectangle. Some puzzles use a drawn shape — a stepped outline, a silhouette, a board with a gap in it. A gap is an area outlined in bold with no grid lines inside: leave it empty. The rules stay the same: cover every square of the shape.
Try It Online
On screen, a tetromino puzzle plays like a set of building blocks: drag a piece from the tray and it clicks into place on the squares, or select it and tap a square or use the arrow keys. Press Rotate (R) or Flip (F) to turn the selected piece when the puzzle allows it, Delete or To tray to take it back off, and Undo to step back. Pieces cannot overlap or cover a starter, and Check confirms the board once every square is filled. Play Tetromino online, and see How to Play Puzzles Online for the general controls.
FAQ
What are the five tetromino shapes?
I (straight), L, O (square), S and T — every way of joining four squares edge to edge, counting mirror images as the same shape.
Do I have to use every piece?
Yes. The bank is the exact set of pieces for that board, and every square must be covered.
Can I flip a piece over?
Only if the puzzle allows turned and flipped — the usual rule when the instructions don’t say otherwise. Turned only allows spinning but not mirroring, and kept as printed means placing each piece exactly as shown.
What do the grey squares mean?
They are starter pieces that are already placed. They stay where they are and help you find the answer.
Can there be more than one answer?
Puzzles made with the one-solution setting have exactly one. Open activity sheets accept any complete covering that uses every piece.
How do I start a child on tetromino puzzles?
Use a small board with three or more starters, allow turning and flipping, and cut the pieces out. Longer boards and the turned-only rule are the next step once the small ones get easy.