Stereo

That's how I expect it works, the light over the USB port that shows what "channel" it's on is also a light sensor. Though it still leaves some questions about pairing things, like what does a light sensor+motor do? Brighter light faster motor? Can you pair 2 single motors to the controller at once, or do the sticks only both work with a 2-motor brick? If Pybricks can communicate to them over bluetooth they seem pretty useful, since the motor brick is now the complete package (bt/battery/motor) in 6x6x3 form. As for fitting that in a train, 9 plates high fits in a 4 wide space when it's on its side, so it'll need a little more vertical clearance than a plain PU battery box (4 bricks tall = 12 plates vs. 6 studs wide = 15 plates), but not much, and since parts of that are 1x4 bricks on the sides, that can be channeled downward inside a 4-wide frame.

I wonder how you 'pair' stuff without a hub, looks like the salmon brick is a controller with 2 axes and the teal ones are motors. Maybe you link them all to a phone, program the network topology and then it sticks?

Chainsaw teeth are 1 plate apart, maybe you could springload one against the round part of the shift fork to hold it in 3 positions.

Yeah, I've made stuff that's hard to assemble and it doesn't need a lot of parts, just density and structures where none of the subcomponents are stable on their own. For example this MOC is completely solid when it's done, but needs a lot of dexterity to get it to that point. And if you want it to be even harder, do like me and build it with 24316 3l axle with stop, instead of 77765 pins.

90s Space and Technic both stick closer to the original limited palette (black, white, red, yellow, blue, grey, maybe green) so probably a lot of subthemes would work depending what you want to make. Just need to come up with large neon windshield parts.

Yeah, seems like a very heavy duty joint with 2 articulations, both using clicks: Numbered in order they appear in images, 1+2 would face each other as the 2 parts of the joint, 3 sticks on either side of 1 with ratcheting functions, and the 4th piece goes through the hole in part 2 to reach the center, where an axle can lock it in. So if you ratchet both #3 parts the same way, the joint bends, and if you ratchet them opposite directions, the 2 joints rotate relative to each other. Hard to be certain about how the 4th part's connected to the 1st but I'm thinking you just run an axle through it. Also would need to see the other side of #3s to know if any connection points exist on the outward facing side. 1st part has features I'm not sure the function of - 8 splines on the inside of the side holes (which goes to smooth parts of the gears), and a pinhole down the center that seems like it should just run into a dead end. Maybe they're just reducing the mass of plastic used.

Odd numbers make more sense on their own - you can combine them to get even numbers, but you can't combine even beams to get an odd length. Inconvenient if you need the span to be a single beam, but usually Technic sets just design for those sizes to be odd numbers I guess.

Price on par with the Orient Express, which I already passed on for a 20% discount recently... I do like the look of this one more. I'm kinda suspecting "can be motorized" means the 2nd/3rd axles of the tender can be a train motor though.

Looks like around 1:12 to me, eyeballing that it's around 5.5 feet long (didn't count the studs cause it's ~190)

If you have an axle stabilizing the middle, you can use 2L liftarms: Nothing else can use the space between the turntable pinholes anyway though (3x3x3, sort of), so maybe it's simpler to just offset the clutch mechanism so it sits in that space instead of in the turntable's ring.

It's originally Orient Express side rods - https://rebrickable.com/parts/4586/technic-beam-1-x-9-thin-with-3-holes/

That one's essentially freely moving. Though there are 2 types of towball, smooth e.g. https://www.bricklink.com/v2/catalog/catalogitem.page?P=15456#T=P which is the intended partner for trailer hitches, and textured e.g. https://www.bricklink.com/v2/catalog/catalogitem.page?P=22890#T=P which is used for posable figures. The textured ones have more friction but not enough to hold any weight. If you put the ball in a pose where the mold lines touch the socket, it will also have a slight stick. Looks like all of them are molded so the mold line is horizontal equator when the piece is studs-up, which avoids hitting this kind of socket if both pieces are facing up.

Hmm, is this only partly completed? The submarine should add a bunch of sand blue, and 1L yellow beams.

It seems about the same gauge as the large Harry Potter train, so you can just run 5 stud wide frame between Lego wheels instead of 4?

Thanks! That seems right, goes with the Downtown Diner figure. Not sure how I missed it searching for "scared" and "open mouth teeth" heads.