Start with a Tic Tac. Finish with the Moon.

A domino can knock over one about half again its size

That's a real result. Lorne Whitehead published it in the American Journal of Physics in 1983. Stephen Morris, a physicist at the University of Toronto, does the famous arithmetic: start with a domino 5 mm tall, make each one 1.5 times bigger, and the 29th is about as tall as the Empire State Building.

So keep going. Your first domino is the size of a Tic Tac, 2 cm. Your last one has to reach the Moon, 384,000 km away. That's a factor of about 19 billion. Each step up is small. About fifty of them is the whole trip.

The catch is that the chain is already falling, and the Moon gives you a minute, plus a second for every PERFECT.

The rule fits on one line

The falling domino's top has to land on or above the next one's black middle line.

You hold to grow the next domino where you pressed. A gold mark shows where the falling domino will hit it. Let go while the middle line is still under the mark and the chain carries on. Hold too long and the falling domino hits it below the line, it stalls, and the run ends: TOO TALL, with the exact miss underneath, like it grew 9% past the gold mark.

The mark moves, and the game's coach line says how: the mark is highest at middle distance: too close has no run-up, too far hits low. Right up close, the biggest domino you can knock over is no taller than the one that's falling. In the sweet spot it's about 1.66 times as tall.

Overshoot by up to 7% and you get a wobble. The target rocks, thinks about it, and goes over a beat late. On screen that's …PHEW.

Small steps lose too

So play it safe, you'd think: grow little ones, never get near the mark. That loses. The chain won't wait for you, and the Moon is the clock. It sets in 60 seconds, and only a PERFECT (letting go within about 11% of the limit) buys a second back.

The game ships with bots that play it on their own. One grows small dominoes on purpose. It ran 200 times and never got past a house. Half its runs ended with THE CHAIN CAUGHT UP. Most of the rest ended with THE MOON SET. The bot that holds right on the line went 0 for 200 too: every run ended TOO TALL.

So the game lives in a narrow band. Let the middle line ride right up to the mark. Not past it.

What fifty dominoes looks like

The camera pulls back on every clack, so the domino you're growing stays about the same size on screen while the world shrinks behind it. Grass, then a cat, then lit houses and a church spire. Then a city, mountains, cloud, and the Earth curving away under a road made of the dominoes that already fell.

Water turns up on the way: a puddle, a pond, a canal, a river, a lake, a sea. You can't stand a domino in water, so you grow a tall one on the near bank to reach across.

Here's one run by the game's best bot, the one that lets go right at the mark:

Its 39 PERFECTs bought back 39 seconds, so the Moon still had 41 left. On a typical step that bot grows each domino about 1.58 times the one before it, which is close to Whitehead's 1.5.

Frames and timings are the game's own bot playing it. The best bot reaches the Moon in 178 of 200 runs.

What's real and what's fudged

• The 1.5 is real. This game is a bit more generous: about 1.66 at the sweet spot, a little more if you wobble. Its title card rounds that up to twice. It isn't twice.
• The falls are sped up. A domino 384,000 km tall would take hours to fall. The game gives it a couple of seconds.
• On screen, the Moon is about 35 times too big.Drawn at its actual size it would be a speck next to the last domino.
• It's arithmetic, not physics. The topple is the one-line rule above plus the run-up limit, so the same press gives the same result every time.

How a run ends

Almost always on a miss you saw coming. The end card names it in one line, tells you how far you got (you toppled 652 m: taller than a skyscraper), and dangles the next thing: a mountain was 2 dominoes away. Click, tap or press Space and you're back at the start with a Tic Tac.

Your best height stays in this browser and shows up as a dashed gold line across the sky on the next run. Cross it and you get NEW BEST!. Reach the Moon and the card says YOU TOPPLED THE MOON, with your dominoes, your seconds and your perfects, and one more line: go again: can you do it in fewer?

Plain answers

What does it cost?

Nothing. No account, no ads, no download. It runs in the browser tab.

Does it work on a phone?

Yes, it's one finger. The screen is laid out wide, so it's bigger with the phone turned sideways. There's no tall phone layout yet.

Keyboard?

Hold and release Space in the full-screen game. Up here on this page, Space scrolls the page instead. It grows the domino where your mouse is pointing, or at the sweet spot if you haven't moved the mouse. R restarts any time.

How hard is it?

Honestly, nobody outside the workshop has played it yet. The best guess comes from a bot built to play like a decent person, a quarter-second slow and a bit sloppy. Over 200 runs it got past a house 72% of the time, past a skyscraper 59%, past the edge of space 44%, and reached the Moon in 47, about one run in four.

Is my best saved?

In this browser only. Clearing your site data clears it.