Tetris

Seven kinds of piece fall one at a time into a ten wide well. Move and turn each one as it falls, and when a row is completely filled it disappears and everything above it drops down. If the stack reaches the top and a new piece has nowhere to go, the game is over.

Pieces come from a shuffled bag of all seven, so you never wait long for a particular shape and a long drought of the same piece cannot happen. The next three pieces are shown on the right so you can plan ahead.

Clearing more rows with one piece is worth far more than clearing them one at a time. Every award is multiplied by your current level.

You move up a level every ten rows. Each level makes the pieces fall faster, following the standard guideline curve, and the music gets quicker with you. By the middle levels a piece crosses the board in under a second, and the top levels leave very little time to think.

A piece that touches down does not lock straight away. It gets half a second to slide or turn, and each move resets that timer, up to fifteen times. That is what lets you tuck a piece into a gap at the last moment.

The ghost piece is the outline at the bottom of the well. It shows where the current piece will land, so you can line it up without counting rows.

Hold is for saving a piece you cannot use yet, usually the long I piece while you build a column for it. The held piece is dimmed once you have used your swap, until the next piece locks.

Turning a piece against a wall or another block does not simply fail. The game tries a short list of small shifts, in a fixed order, and uses the first one that fits. This is the Super Rotation System used by modern Tetris, and it is what makes tricks like sliding a piece under an overhang possible.

The I piece has its own kick table because it is longer, and the square O piece never needs one.

Nothing is downloaded for the audio. Every sound is calculated in your browser and played through the Web Audio API.

The soundtrack is a chiptune arrangement of the Russian folk song Korobeiniki, the tune most people know as the Tetris theme. A square wave plays the melody, a triangle wave plays the bass, and a kick, snare and hi-hat are built from sweeps and filtered noise. It plays only while a game is running and speeds up as you level up.

Moving, turning, locking, clearing rows and levelling up each have their own sound, and a Tetris plays a short fanfare. The speaker button above the board turns all of it off.

Does it save my score? Only your best score, and only in this browser. There is no account and nothing is uploaded.

Does it work on a phone? Yes. Use the six buttons under the board to move, turn, drop and hold.

Can I play full screen? Yes. Pressing Start enters full screen on its own, and the full screen button does the same at any time. Leaving full screen pauses the game.

Why did the game pause by itself? It pauses when the tab is hidden so a piece does not fall while you are away.