I thought 3D Touch was cut because no one seemed to know the functionality existed, it had a discoverability issue. It was kinda tacked onto iOS unlike WatchOS where it was part of how the entire OS was designed.

Which I always found unfortunate, it had some really nice uses like not needing to wait when holding down for the OS to register and being able to pull up a context menu, slide up, and release to select the menu item all in one motion. I was sad when it was removed, but I also get it.

I get the idea of a physical trackpad, and I do remember when that was the thing. I honestly don't even notice that the trackpad is not physically moving. It simulates the feel enough that if I didn't know it was not moving I would think it was. You are right it is shocking when you try to use it while it's off and it's like... oh right. But I just am not in that situation often. (However when Mac freezes and it "clicks" multiple times since it did not properly register ealrier, that's honestly kinda wild... but infrequent).

But I also like not needing to think, I need to press on a specific part of the trackpad for it to properly register. I vividly remember only the bottom half really registering and the higher you went the shallower the press was.

I’m sorry what

You can adjust the pressing force required in software, and the glass does in fact depress under your finger. It’s cushioned - that’s how they detect pressure.

My Apple trackpads don’t click when they are powered off. It just feels like pressing a piece of glass.

You can also detect pressure by just measuring how much of your finger is touching the pad. A small spot means light pressure, a large spot where your skin is flatted out more against the glass is higher pressure. In practice these kinds of measurements are fairly tricky so they don't get used very much.

This. If you ever look at apples raw input touch privateframework it provides enough data for the relative direction/size as well as has some encoded states to at least detect between a very faint touch and a finger on the trackpad.

This I think goes back to the first unibody MacBooks from around 2008.

The multitouch trackpads actually showed up in the early 2008 MacBook Pros that were the last ones before switching to the unibody enclosure (IIRC the keyboard/trackpad parts could be retrofitted into 2007 MacBook Pros). The early 2008 models still had a separate physical button at the bottom of the trackpad. The late 2008 models got rid of the button and made the whole trackpad hinged at the top to act as a button. Then in 2015 they introduced the Force Touch trackpad that fixed the awkwardness of needing more force to click the further up the trackpad you went.

Yep. And this blog post from 2009 was a big inspiration for me in exploring touch on the mac: https://archive.org/details/2009-03-28-steike-code-macbook-m...

and a comment a few years ago by me: https://news.ycombinator.com/item?id=23274577

They barely deflect, strain gauges measure the deflection and trigger the haptic part. When off, it does feel pretty solid. When on, the effect is very convincing, you would never know it's not a button without being told. I had a coworker once that was ready to open up his turned-off macbook because he had been near sand recently and was convinced sand must be trapped inside the trackpad because it "didn't depress".

You can choose three settings instead of an arbitrary level of adjustment with the old screw system. It used to be super easy in the very first round of unibodies, practically tooless except for the screwdriver on the trackpad since the battery came out with a finger latch at the time. Just shut the thing off and try it out, if it had cushioning you'd be able to tell then but its basically a slab of glass.