"What order do you want them in?"

She looks at Afen. "Are you playing?"

" - sure."

These rules say that the youngest player goes first so she doesn't need to know anyone else's relative ages to carefully count cards and arrange the deck, including all of the "draw more cards" cards and "skip turn" cards. She stacks them up with her tongue sticking out the corner of her mouth.

Her grandfather is charmed.

Her parents squeeze each others' hands and giggle.

Predictably, Lintalai wins, grinning like a little blue fox the entire time.

Such a blue! "Okay, I think it's bedtime."

"Why do you think that?"

"Because it is nine."

"Why is nine bedtime?"

"I think if you go to bed at nine you would wake up rested at about the same time as us, and that would be great."

"Okay."

Carry upstairs?

Yes. And then she wants to read The Good Night Book.

The Good Night Book is kind of boring; it describes all the workers in the city and how they go home and hug their babies and go to bed.

"This should be called The Dull Night Book."

"Maybe they are trying to bore you to sleep."

"I am annoyed at it instead."

"Should we read a different one?"

"Yes." She selects Trains.

There are thirty million people in a big city. Every day, most of them will go to work or school or stores. How do you make a city that can move thirty million people?

Trains!

The earliest trains were for shipping materials across the country. Hard-working people laid train tracks stretching the whole continent, so goods could travel much faster than they would in a wagon. These trains were not very good for moving people. They burned fuel and were smelly and loud and expensive. Here is an early train:

Early trains transformed the world. They let us build cities in new places. Before trains, almost all cities were on the water, for shipping. After trains, a city could be anywhere! They were slow and loud and icky, but they soon crisscrossed the world.

And our greens got better at trains. They invented trains that went faster and smoother. Here are some not so early trains. Do you see what's different?

Some people saw that trains had the potential to let us make our cities denser. So they had us build tunnels for the trains to go through. That way, people could get around the city quickly. These trains could not burn fuel- in the tunnels that would be terrible. Instead they run on electricity.

When you are trying to make a city grow, solving one problem just makes more problems! The trains worked great - and so they were too full of people! And so we had to design better trains and better platforms, to move more people around a city. 

How do you change a train to move more people? Well, some cities now have multilevel platforms and two-story trains; you get on the train on the bottom level and get off on the top level, which helps make boarding and unboarding at each stop happen faster. Some trains have more door - the whole side of the train is a door - to accomplish the same thing. Other places have just decided to solve the problem with more trains - digging deeper for more tunnels.

Trains have not just gotten better at carrying people in cities. They've also gotten better at freight - they can haul more, with less fuel - and at taking people long distances. Freight trains usually don't go any faster than they did back when we first invented them. Going faster takes more energy, and that's often not worth it for freight shipments. Long-distance trains for people have gotten more than twenty times faster, though! They can now cross a country in only a few hours. Fast trains mean that people see their families more and switch jobs more easily - and that's really good!

Trains these days don't run on tracks. They run a few different ways. High-speed trains look like this:

This minimizes resistance so they can go really fast.

Modern freight trains look like this:

This is the design that makes it cheapest to move things!

And modern city trains look like this and this:

These designs let lots of people get in and out quickly without slowing each other down!

How would you design a train?

This is pretty cool. "Why is it so good to switch jobs?"

"If it is hard to switch jobs, then if your boss is not nice or you don't like the work or you aren't making much money you have to put up with it. If it's easy to switch jobs then you can find one where you are treated better."

"Then who will do the job you leave?"