Reward Checks

Reward Checks

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About 2 years ago, I learned about Donald Knuth's reward checks. They're checks awarded by Knuth to people who find errors or make substantial suggestions on his published work, typically worth a "hexadecimal dollar" (denoted 0x$1.00), or $2.56. The MIT Technology Review describes them as "among computerdom's most prized trophies."

A reward check for $2.56 from Donald Knuth to Tony Lu from the fictional Bank of San Serriffe.

I love stuff like this. It speaks to Knuth's perfectionism and wit, and it's also just a really fun, unique idea. Feels like a representation of his values and sense of humor that you can also feel when reading his work, like Digital Typography.

Bank of San Serriffe

Knuth's reward checks were real, negotiable checks until he was forced to stop in 2008 because of check fraud:

Leading banks and investment funds have been foundering, because of bad debts and lack of trust; and other, less well-known kinds of fiscal chaos are also on the horizon. For example, due to an unfixable security flaw in the way funds are now transferred electronically, worldwide, it is no longer safe to write personal checks.

Donald Knuth

His solution was to create the fictional Bank of San Serriffe:

After painful deliberation I've come up with a new plan, which I hope will be acceptable to all concerned, and perhaps even welcomed as an improvement. Instead of rewarding heroic bug-finders with dollars, I shall henceforth award brownie points, otherwise known as hexadecimal dollars (0x$). From now on it will be kudos, not escudos.


Instead of writing personal checks, I'll write personal certificates of deposit to each awardee's account at the Bank of San Serriffe, which is an offshore institution that has branches in Blefuscu and Elbonia on the planet Pincus.

Donald Knuth

The bank even has a website maintaining all account balances.

Now, obviously, reading about the Bank of San Serriffe as "someone in crypto," I found great irony in this: one of the greatest computer scientists ever manually maintains balances on a comically large HTML file with pretend money, when it's trivially accomplished with blockchains.

Since basically all of my work is public, and I like creating fully on-chain things, I wanted to make my own 5/9 reward checks: fully on-chain NFTs that I mint to people who submit fixes/suggestions to my work, alongside 5.5ˉ⋅10−55.\bar{5}\cdot10^{-5} ETH. My reward checks obviously don't require fictional banks or pretend money :).

5/9 Reward Checks

I marinated on this idea for 2 years because I didn't have any good inspiration for the design, and there wasn't any urgency to do it. Then, one day, as I finished the 9th interval of a 16×400m workout, I visualized the progress in my head:

16×400m workout visualizationVisualization of the progress of a 16×400m workout, where 9 of the 16 intervals are completed, and 5 of the 9 intervals are randomly highlighted.00000000011111

The green pixels (labeled 0) are completed intervals, and the blue pixels (labeled 1) are a random selection of 5 out of the 9 completed intervals. Visualizing the progress and/or time remaining in a run is something I typically do to mentally chunk it up and make it easier for me to finish. Usually, it's something simple like reducing 16 to 4 sets of 4: "25%, 50%, 75%, 100%" feels more digestible than "6.25%, 12.5%, 18.75%, ..., 100%".

In this case, I don't remember what was going through my mind to conjure up a visualization of 5/9; maybe narcissism or love for myself. Either way, it gave me the idea of generating all 3×3 grids, where 5 out of the 9 pixels are highlighted.

This idea reminded me of Knuth's reward checks because I thought it'd be a fun and representative way to express myself, just like how Knuth is playful with his. The theme and visualization of 5/9 is an obvious reference to my identity, and it's also something I've sprinkled throughout my previous work for fun. All of this connects nicely to the core idea of this being a fully on-chain NFT as well.

Design

I came up with the following as the central element:

A sample 5/9 reward check with the pattern `101010101` highlighted.

I'm pretty happy with this. There's (95)=126{9\choose5}=126 ways to fill the 3×3 grid, which provides enough visual variety amongst reward checks, and I think it looks pretty nice. Apart from the highlighted pixels, I fit in a couple other references to 5/9:

  • The rotated square is exactly 5/9 of the area of the square containing it. You can tell from the grid lines because

(Side of the rotated square)2(Side of the container square)2=12+22232=5232=59\frac{(\text{Side of the rotated square})^{2}}{(\text{Side of the container square})^{2}}=\frac{\sqrt{1^{2}+2^{2}}^{2}}{3^{2}}=\frac{\sqrt{5}^{2}}{3^{2}}=\frac{5}{9}

  • The image is 555×555 pixels.
  • The grid lines are 55px apart.

I was going to just deploy the SVG above as the NFT, but it's a little too ambiguous. Since it's a "check," I wanted something closer to a card with relevant information displayed. When I created Curta's Flag NFTs, I deliberately designed and implemented them in a generic way to display information related to the NFTs. I tested it here and liked the look, so I reused the design and code here:

2 sample 5/9 reward checks side by side.

I haven't deployed the NFT yet, but I will link it here when I do.

Submitting

To submit a fix/suggestion, make a PR on any of my repos or DM me on 𝕏 or Farcaster. If you want a 5/9 reward check, let me know your Ethereum address :).