This is an image-heavy post.

I love Zachtronics. One of their games is Infinifactory (Trailer), a 3D puzzle game where you assemble blocks to form a certain product.

One of the later levels of the game is called "The Big Blowout" (Resistance Campaign → The Heist → The Big Blowout) in which you assemble a bomb-like device that looks like a hollow cube. It's quite difficult to assemble.

I had stopped playing the game a while ago, but someone in my Steam friend list recently asked to see my solution for this puzzle, so I recorded some GIFs using the game's built-in GIF recording feature. This made me re-discover the solution and I thought it was pretty cool so I'm posting it as a blog post.

Solution stats: 327 cycles, 309 footprint, 386 blocks. This is not the best. Here's someone smarter than me doing it in 276 cycles.

Final product

The final product appears to be a bomb-like cube. It is hollow in the middle and all 4 sides have a hollow center with grey edges. The top and bottom are all black blocks with an orange center.

Overall structure

The level is made of 2 stages linked by a single-block (purple) teleporter. This is the most significant limiting factor of the level. You cannot teleport more than one block per cycle through the teleporter. Thus, the main factor that determines the solution's speed is how highly utilized the teleporter cube is, i.e. the percentage of cycles during which the solution is using the teleporter cube to teleport a block.

To this end, the solution tries to build a single long chain of blocks that correspond to exactly one unit of the final product, then pushes this chain all at once through the teleporter. Because all the blocks are aligned in a chain, no cycle is wasted from block to block. While the chain is being pushed, the next chain is being assembled right above the chain being pushed. Once the first chain is fully through the teleporter block, the next chain falls right into the conveyor belt and is then pushed it through the teleporter, and so on.

The other side of the teleporter is not very surprising. A redistributor first first lines up all the blocks from the chain in the same order as they arrived in through the teleporter. Once the chain is fully teleported, all blocks are pushed aside simultaneously in order to immediately make room for the next chain coming in through the teleporter. From there, the pushed-aside blocks get split up into multiple assembly lines that progressively weld everything together until the final product is assembled.

Big picture

Here's an overall view of the solution.

Initial extraction & teleporter chain:

Redistributor on the other side of the teleporter:

Re-assembly lines:

Details

Initial resource extraction

This section extracts the cubes from the dispensing containers at the beginning of the level. It tries to be as non-blocking as possible, which is necessary in order to sustain enough extraction throughput to be able to build a new chain of black blocks by the time the previous one is fully teleported. The main challenge are the black blocks (because the final product requires a lot of them), so the chain-building happens alongside the same line as the one directly taken by the black block dispensing container.

Teleporting the chain

This section buffers a chain of one product's worth of materials, then pushes it into the teleporter cube while buffering materials for the next chain.

Redistributor

This section receives the chain from the teleporter. Once it is fully received, it pushes all blocks aside simultaneously to make room for the next chain to arrive through the teleporter. Blocks are pushed into distinct assembly lines.

Lower conveyor

This section assembles the lower layer of the final product.

Middle conveyor

This section assembles the middle layer of the final product, and brings extra black blocks to both the upper and the lower conveyors.

Upper conveyor

This section assembles the top layer of the final product.

Putting it all together

The middle conveyor drops the grey blocks onto the bottom conveyor to build the first 2 layers of the final product:

Once assembled, the resulting partial product is brought back upwards to be on the same height as the product receptacle:

The top conveyor drops the components of the top layer onto the partial product.

Finally, the finished product is conveyed to the product receptacle.

Bonus

Since you're still here, here are a few mesmerizing GIFs from Zachtronics's latest game, Opus Magnum.

Conclusion

I am not affiliated with Zachtronics, I just love their games. You should buy them. They are available DRM-free on Steam and GOG for reasonable prices and they all work on Linux.