Here's how it works. You get five different numbers from a number pool 1 to 20, and a target from the remaining pool. Combine two at a time with + − × ÷, using all five numbers, every result a positive whole number, each puzzle always takes 4 moves. You get 3 rounds and 4 undos per round; a medal for fewest moves (perfect 4 = crown). There's a spoiler-free share card, like Wordle’s grid.
The combinatorics math works out like this: C(20,5) (that's choose 5 from 20) × 15 possible target numbers = 232,560 possible puzzles. An interesting side quest: exhaustive search discovered that exactly 6 can’t be solved. They all are from the group of 6 numbers: 3, 7, 16, 17, 19, 20. If any one of those is chosen as the target the other 5 cannot make the target. I'm not sure if there are any interesting reasons or patterns.
Every puzzle was sorted into 7 difficulty bands, by how many solutions each has, to provide a way to add increasing difficulty along the week. Sunday draws from the easiest 30%, Saturday from the hardest 3%, the game shows “harder than X% of puzzles” on the hardest days; Saturdays so far have been in the 98th–99th percentile of difficulty. 5 Saturdays were discovered to have exactly one answer (answer here means ways that only regroup or reorder the same moves count as one); the first is #68, Saturday, December 19, 2026.
A few things I'd love to know from y'all:
Difficulty: does the Sunday-to-Saturday curve feel right, and are Saturdays too hard? I've experimented with a mode that offers some help. But it's still under development.
First-time play: was anything confusing, like dragging vs. tapping or how rounds work?
Phones: How does it play on your phone vs your computer?