Ultracube is the most creative overhaul mod for Factorio I’ve played yet. You start with a single item: the cube. You never get another one. This cube is required as a catalyst for fundamental bulk production of power and material.

This limitation means factories cannot be scaled in the traditional manner. Instead the focus is on optimising “cube uptime” in shunting it between operations.

In addition, there are many unique challenges in the later game requiring a decent amount of circuitry expertise. I found these really fun but they were certainly more difficult that in any other mod I’ve tried. This is a hard mod overall, though short for an overhaul: I completed it in just under 30 hours.

I loved the theme and flavour text. Joyful, irreverent, but internally consistent and aided in understanding.

While many (all?) assets were reused from vanilla and Krastorio 2, they were used in very different ways which made my factory feel even more unique. For example, fabricators instead of assemblers, red belt from the outset, and the first “basic matter” material used the plastic icon.

This mod is still under active development. I kept a list of “annoyances” while playing but virtually all of them have been fixed by the time I write this so not worth sharing. The main unfixable issue relates to not being able to load bulk recipes while they still have output: this covered in the FAQ, and can be worked around adequately with Inventory Sensor, which I would consider a required mod anyway: getting reasonable cube efficiency without it would be unnecessarily painful. (The documentation for that mod is lacking: you need to place it with the green/red terminals facing away from the assembler otherwise it won’t work.)

Technologies were not revealed until researching the relevant science card, a touch I really appreciated. I never knew what was coming next and it was always a nice surprise. More mods should do this.

I used Alien Biomes but didn’t check my map settings and generated a world with no trees. Wood isn’t needed in early game so didn’t think anything of it, but is required to bootstrap something in the mid-game, which was too late to restart. I console cheated the needed catalyst.

Mods

In addition to my standard quality-of-life mods, I tried two new mods this run:

• Wire Shortcuts. Circuit wires don’t need to be crafted. Probably going to use this on all future runs, making circuit wires always felt like a chore.
• Picker Dollies. Shunt entities without picking them up, keeping their wire connections. Invaluable in particular for combinators. Adopting for all future runs.
• Inventory Sensor. Mentioned above, would be pretty niche in other mods but likely useful to have.

Minor Spoilers

Only read this section if you’ve already played it yourself! This mod really is a treat to figure out on your own.

• I never really figured out a good way to use the alternative basic matter and component recipes unlocked with T3 phantom cubes. Have a nagging feeling I’ve missed something interesting. (Not just me it seems.)
• Seeing my first cube-powered train zoom off was a genuine moment of unexpected delight.
• Qubit processing was my favourite puzzle. I was afraid it was going to be like arcospheres from Space Exploration, but it was a completely different non-trivial combinator problem with none of the frustrations of arcospheres.
• The Cyclotron was confusing, it looks like it is unpowered even when it is. It does operate how the description text says though (80s delay). I solved it with a timer circuit which I think is the intended solution, it just took me a while to realise I was supposed to build it myself. Fun little challenge.
• Uranium processing adds a new element but to me it still played exactly the same as vanilla so felt a bit like extra complexity for no new challenge.
• The final Ziggurat reconstruction challenge was tough but ultimately rewarding. I needed a few tries to get it right. It’s possible to fail hard here, ending in state where you can’t reconstruct the cube. Would have liked some warning, since I don’t think that’s ever been the case in any other mod. I had to reload a couple of times. I was surprised when the victory screen popped up on success, but apparently that’s changed in recent versions to something that feels a bit more natural.
• The power generation option unlocked at T6 feels too late: I already had to scale up power massively (annoyingly) for the Ziggurat to get there … and I’ve already been shown a victory screen. (This might be fixed in later versions? Not sure.)
• I never got to playing with the Mystery Furnace. Will need to go back in…

I created a mapshot of the factory for posterity, where you can scroll and zoom around. This is a fantastic mod that everyone should try.