OneTaskBy Tim King · Updated
Jenga 3D
Pull Blocks From a Physics Tower in Your Browser
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How the 3D Jenga works
This Jenga 3D game is played with real physics. The tower is stacked three blocks to a layer, each layer turned ninety degrees from the one below, just like the real game. Click any block to shove it out along its length, or press Pull a random one and let the tool choose. Every push shifts the weight above it, and the stats track how many blocks you have pulled, how tall the tower still is and how many blocks have hit the table. When enough of it comes down the status line tells you how many pulls it lasted. Drag to orbit, scroll to zoom, Save PNG to keep the wreckage.
Jenga was designed by Leslie Scott, who launched it at the London Toy Fair in 1983. The name comes from kujenga, Swahili for "to build". A standard set has 54 wooden blocks stacked 18 layers high, three to a layer, each layer at right angles to the one below. Players take turns pulling a block from anywhere below the top and placing it on top, and whoever brings the tower down loses. It looks like a game of steady hands. Underneath, it is a game of friction and centre of mass.
Playing Jenga 3D in your browser
Every block here is a separate rigid body in the Rapier physics engine, with its own weight and friction. Nothing is scripted: the tower leans, slides and falls for the same reasons a wooden one does. The blocks keep the real proportions of 1 : 1.67 : 5, and the default of 18 layers gives the standard 54 blocks.
Click a block to push it along its length. Pull a random one picks a block for you from the middle of the tower, skipping the bottom two layers and the top layer or so, as house rules usually do. There is no "place on top" step; the game is purely about how many blocks you can take out before the tower goes.
Why the tower stays up
A block does not need all three supports beneath it. The tower stands as long as the combined weight above each layer sits over whatever is left of that layer. That leads to the rules of thumb every good player uses:
| Layer state | Stability | Why |
|---|---|---|
| All three blocks | Solid | Load spread across the full width |
| Middle block gone | Still solid | The two outer blocks carry the load evenly |
| One outer block gone | Risky | The centre of mass shifts towards the gap |
| Only one outer block | Very risky | The layer above balances on an edge |
| Only the middle block | Balancing act | Stable only if the tower above is perfectly centred |
The middle block is usually the safest first pull because it leaves a symmetrical layer. Taking both outer blocks from one layer leaves the whole tower above resting on a strip one third the width, which only works while nothing leans.
Friction is the other half. Real Jenga blocks vary very slightly in thickness, so in any layer one or two blocks carry most of the weight and the loose one slides out easily. Experienced players tap blocks to find the loose one rather than pulling the first they see.
The settings
- Layers runs from 6 to 30. A short tower is very hard to topple; a 30-layer tower is nervous from the first pull, because a small lean at the base becomes a large offset at the top.
- Stacking sloppiness shifts each block by a small random amount so the tower is not perfectly square. At 0 the blocks line up exactly and the tower can survive a surprising number of pulls. Near the top of the range it looks like a rushed stack and may sag before you touch it. This stands in for the uneven thickness of real blocks.
- Push strength sets how fast each click sends a block, from 1 to 8 m/s. A gentle push slides it partway out and leaves it hanging, loading the tower unevenly. A hard push fires it clean across the table, but the friction jolt can drag the layers above it along too.
Reading the stats
- Blocks pulled counts every block you have pushed, including any that stuck partway out.
- Tower height is the height in layers of the highest block still near the centre of the table. It drops when the top slides off, even if most of the tower is still standing.
- On the table counts blocks that have ended up away from the tower's footprint. Once more than 30 % of blocks are out there, the game declares the tower fallen and tells you after how many pulls.
- Moving is how many blocks are still in motion. Wait for it to reach 0 before your next pull, or you will be pulling from a tower that has not settled.
Tips
- Start in the middle of the tower. The bottom layers carry the most weight, so their blocks are gripped hardest, and the top layers have little weight to keep them steady.
- Try a middle block first. It leaves a symmetrical layer behind.
- Lower the push strength as the tower thins. Once most layers are down to one or two blocks, every shove passes a jolt up the stack.
- Use sloppiness as a difficulty setting. Zero is practice mode; 0.15 or higher is a real challenge.
Related physics toys
Knock a tower down all at once with the wrecking ball simulator, set up a chain reaction with 3D domino toppling, or stack your own shapes in the 3D physics sandbox.
Restart stacks a fresh tower with the current settings. Everything runs in your browser; nothing is uploaded.
FAQ
Which blocks are safest to pull?
Middle blocks, from layers well below the top. Pulling a middle block leaves the two outer blocks carrying the load evenly; pulling an outer block turns the layer into a lever.
Why did the tower fall before I touched it?
Stacking sloppiness is high. Lower it towards zero for a square tower, or accept it as the game: a rushed stack sags on its own.
Why does a hard push bring the tower down?
The jolt from a block firing out shifts everything above it sideways. Use a gentle push to slide the block partway and then push again, which is how real players do it.
Can two people play?
Take turns clicking. The pulls counter is shared, so note whose turn it was when the tower goes. The usual rule is that the player who made the last pull before the collapse loses.
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