What the lesson actually wanted
The Calculator project sits near the end of the JavaScript Basics section, right after the lesson on objects. The ask is simple on paper, a working four function calculator, numbers, operators, an equals button, handled correctly. Really it's checking whether you can keep track of state using objects instead of a pile of separate variables everywhere.
Why I kept going
I work as a journeyman laborer alongside all this coding stuff, and concrete math comes up constantly on site. Figuring yards for a slab, counting bags, converting between imperial and metric. Normally that's whatever calculator app happens to be on my phone, and it forgets everything the second you close it. Once I had the basic calculator working from the course project, the actual math logic was already sitting there. What was missing was the concrete specific stuff, slab volume, bag yield conversions, and a layout that made sense to use standing on a jobsite instead of sitting at a desk.
It also had to work without signal, since not every jobsite has decent service. That's what pushed it toward being a PWA, something installable that works offline and doesn't care whether you've got a connection.
Where it's at now
GlovesOn is its own offline PWA now, a concrete calculator and unit converter you can install on your phone and use with no signal at all. It came from the same place as TTDice honestly. The course project just gets you to a working skill. What you build with it after that is up to you, based on whatever you actually run into day to day.
GlovesOn is free to use, installs right to your phone, and works offline.
Try GlovesOn