Chain Reaction — a free physics puzzle game with 36 levels

Chain Reaction is a browser physics puzzle you set up once and then watch. Every level is a still scene — ramps, dominoes, levers, balloons, fans, explosive barrels — with one target object and one goal zone. You drag a small inventory of pieces out of the tray, press Space or the Start button once, and after that you steer nothing: a Matter.js simulation on a fixed 16.666 ms timestep does the rest. All 36 levels ship in three chapters, and each one was verified solvable by replaying a recorded solution through the same physics the game runs. Controls are a mouse drag or a finger drag to place, scroll or pinch to zoom, R to rotate, and Space to start or rewind. The whole page is about 63 KB gzipped, it runs offline after the first load, and no account is required.

Pick a difficulty, then play

Each tier changes what the game actually hands you and what it takes away. You can switch at any time from the pause menu, and every tier keeps its own solved levels, stars and best piece counts.

Difficulty Sprout Double the pieces, no timer, no way to lose, and a two-second preview of what your setup will do before every run. Casual One spare piece on every level and three preview runs to spend, with unlimited attempts. Standard — default Exactly the pieces the level was designed around, no previews, and as many attempts as you want. Brutal Only the minimum pieces a solution needs, no slow motion, and three attempts per level. Inferno One attempt per level and 60 seconds to place your pieces, with no rewind and no slow motion; a failure sends you back to the start of the chapter.

No levels solved yet.

Chain Reaction needs JavaScript to run its physics simulation. The rules, the difficulty tiers and the answers below are all readable without it.

How to Play

Read the scene. One object is the target and one marked area is the goal. Nothing in the scene moves until you say so.
Drag pieces from the tray. Mouse, finger or keyboard — press Enter on a tray item, move it with the arrow keys, and press Enter again to drop it. Press R to rotate a piece that can turn.
Zoom if you need to. Scroll the wheel or pinch with two fingers. The camera also follows the action on its own once a run starts.
Press Space once. That starts the run. From that moment you are a spectator: no steering, no nudging, no second chances mid-run.
Rewind and rethink. Press Space again to snap back to your setup with the pieces exactly where you left them, then move one thing and try again.
Chase the star. Every level shows the smallest number of pieces a solution needs. Solve it with that many or fewer and you earn its star.

What the five difficulty tiers change

Sprout — Double the pieces, no timer, no way to lose, and a two-second preview of what your setup will do before every run.
Casual — One spare piece on every level and three preview runs to spend, with unlimited attempts.
Standard — Exactly the pieces the level was designed around, no previews, and as many attempts as you want. This is the default.
Brutal — Only the minimum pieces a solution needs, no slow motion, and three attempts per level.
Inferno — One attempt per level and 60 seconds to place your pieces, with no rewind and no slow motion; a failure sends you back to the start of the chapter.

Switch tiers whenever you like from the pause menu. Solved levels, stars and best piece counts are recorded separately for each tier, and every count shown in the game is labeled with the tier it belongs to.

The three chapters

Chapter 1 — Topple (levels 1–12) builds from planks and rolling balls up to the lever: a beam pinned through its middle that turns a dropped weight into a slide. Levels 1 to 6 carry no text at all; the scene is the whole lesson.
Chapter 2 — Lift (levels 13–24) introduces the balloon, which pulls upward and ties its own string to whatever it is resting against, together with the fan that pushes sideways.
Chapter 3 — Blast (levels 25–36) introduces the explosive barrel, which goes off when something hits it hard enough and shatters crates within its radius.

Features

36 hand-authored levels in three chapters, every one verified solvable by replaying a recorded solution through the shipping physics.
Deterministic simulation on a fixed 16.666 ms timestep with a seeded random generator, so the same setup always produces the same run.
Seven kinds of scene element — planks, balls, dominoes, fixed ramps, balloons, fans and explosive barrels — plus crates and levers that react to all of them.
Five difficulty tiers from Sprout to Inferno, each with its own saved progress and its own best piece counts.
Ghost path previews drawn by the same simulation that runs the real attempt, so a preview can never mislead you.
Slow motion at 0.3x and a one-key rewind straight back to your setup.
Synthesized sound — impacts are pitched by how hard they land, generated with the Web Audio API rather than downloaded.
Paper-craft artwork drawn procedurally on canvas: warm cream paper, thick ink outlines and flat cut-paper shadows, with no image files to download.
Fully keyboard operable, with visible focus rings, WCAG 2.1 AA text contrast, and full respect for the reduce-motion setting.
Runs offline after the first load, stores progress only in your own browser, and never sends your play data anywhere.

Frequently Asked Questions

Is Chain Reaction free, and do I need an account?

Chain Reaction is completely free and there is no account, no sign-up, and no payment of any kind. Open the page and the difficulty picker is already waiting for you. There are no ads, no paywalled chapters, and no timers that ask you to come back later. All 36 levels are unlocked from the first visit, so you can pick any tier and play the whole game in one sitting.

How do I play Chain Reaction?

Every level is a static scene with one target object and one goal zone. Drag pieces out of the tray at the bottom and drop them into the scene, press Space or the Start button once, and then watch: you do not steer anything after the run begins. Scroll or pinch to zoom the camera, press R to rotate a held piece, and press Space again to rewind to your setup and try a different arrangement. The whole game is playable from the keyboard alone.

Which difficulty tier should I choose?

Sprout doubles the pieces the level hands you, removes every timer, makes it impossible to lose, and plays a two-second ghost preview of your setup before every run. Casual adds one spare piece on every level and gives you three preview runs to spend, with unlimited attempts. Standard hands you exactly the pieces the level was designed around, with no previews and unlimited attempts. Brutal gives you only the minimum pieces a solution needs, turns slow motion off, and allows three attempts per level. Inferno gives you one attempt per level and 60 seconds to place your pieces, with no rewind and no slow motion, and a failure sends you back to the start of the chapter. You can switch tiers at any time from the pause menu, and each tier keeps its own solved levels, stars and best piece counts.

Why does the same setup always produce the same result?

The simulation runs on a fixed timestep of 16.666 milliseconds and every random number it uses comes from a seeded generator, so the physics never depends on your frame rate or your device. Replaying a level with the pieces in the same places gives you the same collisions in the same order, every time. That is also why the ghost preview can be trusted: it is produced by the same simulation code that runs the real attempt, not an approximation of it.

How was this game made?

Chain Reaction was generated from a single prompt on Quodara, an AI agent platform that turns one written description into a deployed web app. The prompt described the physics, the piece catalog, the three chapters, the five difficulty tiers, and the SEO requirements, and Quodara authored the 36 levels, the deterministic simulation, the page and the server, then deployed it to this domain. You can read the case study, including the prompt that produced it, at the Chain Reaction case study.

About this build

This whole game — the 36 levels, the deterministic Matter.js simulation, the paper-craft renderer, this page and the Python server behind it — was generated from a single prompt on Quodara on August 22, 2026. The home page transfers about 63 KB gzipped in total, of which roughly 52 KB is JavaScript, and there are no third-party scripts blocking the first paint. Nothing here is a template: the level geometry was authored by a generator script and then machine-verified, level by level, against the physics that ships. The full write-up, including the prompt itself, is at quodara-ai.com/showcase/chain-reaction.