Rewinda and Samesby
a fair race you can check
Loading audio…
Press play to listen along. The line being read lights up as you go.
Show full transcript
Loading transcript…
On the first warm day of summer, the League Field holds its friendly race day. No trophies, no leaderboard of names. Just pairs of friends racing on boards, and two helpers who make sure every race is fair: Samesby the penguin and Rewinda the squirrel.
Samesby waddles up to each pair with his two identical boards held high in his flippers. Rewinda follows behind with her little film reel, ready to spin it.
"Samesby makes it fair," the players say. "Rewinda makes it true."
This year, two young beavers named Twig and Dam signed up to race each other. They had been friends for years and rivals for about a week.
Samesby tapped out a race code and handed it to them both. "Type this in," he said cheerfully. "You'll each get exactly the same board. Same mines, same numbers, same free opening. Whatever happens, it's all about how you play."
They typed it in. Two identical boards appeared. The race began.
It was close. Twig was quick, flying through the easy parts. Dam was careful, slower at first, but never wasting a click. Near the end, Dam found a clever chord and opened a whole ring of squares at once. Dam finished first, just barely.
"I won!" Dam shouted.
Twig's tail slapped the ground. "No way. You must have gotten lucky. Or you did something weird. I don't believe it."
Dam's face fell. Winning had felt wonderful for exactly two seconds, and now it felt like something was being taken away.
That's when Rewinda scampered forward and gave her reel a spin. "Nobody needs to argue," she said. "Dam, the League gave you a replay token when you finished. Can I have it?"
Dam handed it over. It was a short string of letters and numbers.
"This token holds the race board's seed and every move Dam made, in order," Rewinda explained. "Let's re-play it. Not trust it, not doubt it. Just watch."
She fed the token back in. The League rebuilt the very same board from the seed, the board Samesby's code had made, and re-played Dam's moves one by one. Open. Open. Flag. Chord. The board cleared itself, step by step, until the last square flipped. The result appeared: cleared, with exactly the clicks Dam had said.
Twig watched the whole thing, and slowly the anger faded. "So you really did it," Twig said. "On the same board as me."
"On the same board," said Samesby.
"And we checked it," said Rewinda.
Twig looked at Dam for a long moment. Then, surprising everyone, Twig grinned. "That chord at the end was amazing. Can you show me how you spotted it?"
Dam's face lit up again. The two of them bent over the board together, and Rewinda re-played the ending one more time, slowly, so Twig could see.
Samesby beamed at Rewinda. "A fair board and a real check. That's the whole recipe."
"And then friends again," said Rewinda, spinning her reel with a flourish.
Samesby and Rewinda feel most like themselves at the end of a race, when the replay matches and two rivals turn back into friends. It is a sunny, easy, everything-is-settled feeling, like a game of tag ending in a heap of laughter on warm grass.
You have a bit of both of them in you whenever you make a contest fair and let the moves prove the result. Say it the way they do: "Samesby gives the same board, Rewinda re-plays the moves: a fair race, checked for real."
Then race your friend, and check it together.
Hear it as an audio drama
A short play starring Rewinda and Samesby, from Sweep League. Different voices, same idea. Listen any time after you read.
Loading audio…
Read the drama script
- Narrator: From Spark and Anvil and Sweep League — this is Rewinda and Samesby, in chapter 1 of the Sweep League cast.
- Narrator: This drama uses an AI-generated voice. Voiced via Gemini 2.5.
- Narrator: On race day, Samesby the penguin carried two identical boards, and Rewinda the squirrel followed with her film reel.
- Samesby: Here's your race code. You'll both get exactly the same board.
- Narrator: Twig and Dam raced. Dam found a clever chord and finished first, just barely.
- Dam: I won!
- Twig: No way. You must have done something weird.
- Rewinda: Nobody needs to argue. Dam, may I have your replay token?
- Narrator: The League rebuilt the same race board and re-played every one of Dam's moves. The result matched exactly.
- Twig: So you really did it, on the same board as me.
- Samesby: Fair board.
- Rewinda: And checked for real.
- Twig: That chord was amazing. Can you show me how you spotted it?
- Narrator: Same board, re-played moves: a fair race, checked for real. That's their idea.
- Narrator: You've been listening to a Spark and Anvil chapter, written by the Spark and Anvil writing team for ages 9 to 14.
- Narrator: Apps stay free forever.
- Narrator: Curriculum aligned to Common Core and Next Generation Science Standards.
- Narrator: Released under Creative Commons BY-NC-SA 4.0 for educational reuse. Visit Spark and Anvil for the full transcript.
The Sweep League ensemble
Rewinda and Samesby is one of the friends in Sweep League. Each friend shows you one idea by how they act; meet them all and you have the whole subject.
-
Surefoot
only steps where she is SURE; asks which square the numbers prove
-
Bevvy
A bee who knows the fewest clicks a board could take - its 3BV
-
Clicksy
A cricket who counts every wasted click - efficiency is 3BV divided by clicks
-
Oddsley
An owl who weighs every arrangement the numbers allow - the exact odds of a mine
-
Chordy
A crab who opens a whole ring of squares at once when a number's mines are all flagged
-
Floody
A duck who knows a zero opens its whole empty region in one go
-
Knowsley
A red panda who knows every board can be solved by knowing, never by guessing
-
Rewinda
A squirrel who checks a run by re-playing every move, never by trusting it
-
Samesby
A penguin who knows a race code gives both racers exactly the same board
-
Sumsy
A hamster who knows the total number of mines shapes the odds of every hidden square
-
Tickwell
A hare who knows your speed is shown only AFTER you finish, never while you play
