What is PETRIS?
PETRIS is a free browser puzzle game that takes the classic falling-block formula and replaces the geometry with personalities. Instead of seven colored tetrominoes, four single-cell pieces drop into a seven-by-fourteen wooden grid: a dog, a cat, a mouse, and a brick wall. Your goal is to stack three of the same animal in a vertical column to score a pop, fill a horizontal row for a clear, and chain these together for combo multipliers — all without letting incompatible animals touch each other.
The twist that makes PETRIS its own game is the friendship system. Cats and mice clash. Cats and dogs clash. Dogs and mice are friends. The wall is friends with everyone. A piece dropped next to a clashing neighbor is rejected — you see a red flash, hear a hiss, and lose a life. So the question on every turn isn't just "where do I place this piece" but "where can I place this piece such that it doesn't anger the neighborhood." It is, as the About page puts it, less Tetris and more an awkward dinner-party seating chart.
The game runs entirely in your browser. There is no download, no install, no account, no login. You can play it on a phone, a tablet, or a desktop. Your high score is saved locally in your browser between sessions. Pages weigh around fifty kilobytes — the whole experience loads in under a second on a 4G connection.
The Four Animals
The roster is intentionally short. A long list of unit types would have made the game harder to learn without making it deeper. Four pieces is enough to produce real tactical complexity through their interaction.
🐶 Dog — the easygoing one
Dogs are the most flexible piece in PETRIS. They are friends with other dogs and friends with mice. The only animal they cannot tolerate is the cat. Because dogs and mice make up most of the friendly side of the board, you can stack them freely in the center and along the bottom rows without worrying about clashes. Dogs are usually the workhorse pieces that build the bulk of your column-pop setups.
🐱 Cat — the picky one
Cats are the source of more game-overs than every other piece combined. They tolerate only their own kind. A cat next to a dog clashes. A cat next to a mouse clashes. A cat in the wrong column at the wrong moment ends the run. The standard advanced strategy is to dedicate one or two edge columns of the board exclusively to cats, fenced off by walls, so cats always have somewhere safe to land.
🐭 Mouse — the friendly one
Mice share their friendship rules with dogs: they are friends with other mice and with dogs, and they are terrified of cats. Mice are slightly smaller in the artwork and have pink-toned features. Functionally they behave identically to dogs from a clash perspective, which means you can mix dogs and mice freely in the central play area to build complex pop chains.
🧱 Wall — the peacemaker
The wall is the most strategically important piece in the game even though it does not score on its own. Walls do not pop in vertical threes and they contribute to row clears only by occupying a cell. What they do is separate. A wall placed between a cat column and a dog-and-mouse zone breaks the clash check — neither side can see the other anymore. Players who treat the wall as filler die around level three. Players who treat it as a fence routinely clear level seven.
Scoring at a Glance
You score in two ways. A vertical pop happens when three of the same animal stack in a column; the three cells clear and you earn seventy points per cleared cell. A row clear happens when a horizontal row fills completely; the row clears and you earn a flat two hundred points. The two interact: a row clear shifts cells downward, which can trigger a pop, which can trigger another row clear, and so on. Each link in this chain raises the combo multiplier on the next event. A single careful setup can be worth several thousand points.
Walls count toward row clears but never toward pops. They are scaffolding, not scoring pieces — a fact that confuses some players for the first few rounds. Once you internalize it, you stop trying to "pop" wall columns and start using them deliberately.
The Lives System
Each level starts with a fixed number of lives. Level one gives you five, level two gives you four, level three gives you three, level four gives you two, and from level five onward you have exactly one life per level. A single rejected piece — a cat dropped next to a mouse, say — ends the level. If you survive a one-life level, you advance to the next one and your life counter resets. The high-level metagame becomes a question of how many one-life levels you can string together in a single run.
The falling speed also accelerates with each level. Early levels feel meditative; by level four you have only a few seconds to decide where each piece lands; by level seven, hard-drops become a tactical choice rather than a convenience. Players coming from traditional Tetris often find PETRIS's late-game pace easier than expected — but the one-life constraint makes up for it.
Controls
On desktop, the keyboard handles everything. Use the left and right arrow keys (or A and D) to move the falling piece between columns. Press up (or W) to cycle the piece between dog, cat, mouse, and wall — this is free as long as the piece hasn't landed yet, so you can change your mind right up until the lock. Hold down (or S) for a soft drop that accelerates the fall, or hit the space bar for an instant hard drop. The hint line under the board reminds you of all of this.
On mobile, touch buttons appear below the playfield. You can also swipe directly across the playfield itself — left and right swipes move the piece, an upward swipe cycles the animal type, and a downward swipe is a hard drop. The touch controls scale to the screen and work in both portrait and landscape orientation. The game is fully playable on phones as small as 360 pixels wide.
A Short History of Falling-Block Puzzles
The falling-block puzzle is one of the oldest still-living video game genres. The original example, written in 1984, established a template that has barely changed in forty years: a vertical playfield, pieces falling from the top, the player rotating and shifting each piece into place, and rows clearing when filled. The genre has spawned thousands of variants — block-matching games, dropping-fruit games, color-chain games, gravity-puzzle games — but the underlying loop has remained remarkably stable.
PETRIS belongs to a small subset of the genre that swaps the geometric constraint for a social one. Instead of asking "does this shape fit in this space," it asks "does this piece tolerate its neighbors." Other games have toyed with the idea — color-matching puzzles do something similar at the level of identity rather than placement — but PETRIS commits more fully than most. The board state is governed by friendship rules, not by physics. The wall, which is the only purely geometric piece in the game, exists to bridge the two design philosophies: it is what you place when the social rules become inconvenient.
The cozy wooden aesthetic is also a deliberate departure from genre norms. Most falling-block puzzles favor sterile arcade-style backgrounds or hyper-modern minimalism. PETRIS sits in a warm walnut frame with parchment-cream text and faint grain noise, evoking a handmade puzzle box rather than a slot machine. The visual language tells you the game is patient and forgiving, even when the late levels are not.
Accessibility Notes
PETRIS is designed to be playable without sound. There is no audio cue you need to react to — every piece of important feedback is visual. The clash flash, the pop animation, the combo banner, the score popups, and the lives indicator all communicate state through color and motion rather than through audio.
The animal pieces are distinguished by both color and shape. Dogs are blue with floppy ears, cats are orange with triangular ears and whiskers, mice are pink with round ears and a long tail, walls are brick-textured red-brown. Players with color-vision differences can distinguish all four pieces by silhouette alone. The wall, in particular, is the only non-animal piece in the game and reads as clearly different even at a glance.
The game does not use rapid flashing effects, strobing, or screen-shake. Particle effects on pops and clears are short and confined to the cleared cells. The combo banner fades in and out smoothly without sudden movement.
Frequently Asked Questions
Is PETRIS free?
Yes. The game runs entirely in your browser, requires no account or install, and has no in-app purchases. It is supported by a single banner ad slot at the bottom of pages.
Does the game save my high score?
Yes. Your best score is stored in your browser's local storage and persists across sessions on the same device and browser. Clearing your browser data will reset it, and the score does not sync between devices.
Why is my piece being rejected?
Because it would land directly next to a clashing animal — vertically or horizontally, not diagonally. The four cells touching the landing square are checked. A cat next to a dog or mouse, or a mouse next to a cat, will be rejected. Dogs and mice are friends with each other, walls are friends with everyone, and identical animals are always friends.
Do walls ever pop?
No. Three walls stacked in a column will sit there indefinitely. Walls only contribute to scoring by filling out a complete horizontal row.
What's the highest possible score?
There is no fixed ceiling. The level counter and speed continue to scale indefinitely, but in practice the one-life constraint past level five makes runs above twenty thousand points extremely rare. The leaderboard for PETRIS is your own — beat your previous best.
Can I play on mobile?
Yes. The game detects touch input and shows on-screen buttons under the board. Swipe gestures across the playfield also work. The board scales to fit any screen size from small phones to large tablets.
Why "PETRIS"?
It's a portmanteau of "pet" and the name of the foundational falling-block puzzle. It also doubles as a Latin-flavored play on petrus, a stone — appropriate for a game whose most important piece is a brick wall.
Where to Go Next
If you want the full mechanical breakdown — controls, scoring, combos, the lives table — read the How to Play guide. If you've already played a dozen rounds and want to push past level five, the Strategy page covers wall placement, combo chains, and cat discipline. The About page covers the design thinking and how the game was built. Or just hit the Play button above and start a fresh run.