Natural Number Game
Shares rank 14 of 24 online tutorials by recommenders
Free game that teaches Lean by proving basic facts about natural numbers, praised as a strong start to Lean. Caveat: some tactics and semantics are poorly explained.
Free game that teaches Lean by proving basic facts about natural numbers, praised as a strong start to Lean. Caveat: some tactics and semantics are poorly explained.
6 people gave an opinion
- recommend it
- 6
- criticize it
- 0
- approval share
- 100%
Recommended in 4 of 13 months
- November 2025: not recommended
- December 2025: not recommended
- January 2026: recommended
- February 2026: not recommended
- March 2026: not recommended
- April 2026: recommended
- May 2026: not recommended
- June 2026: not recommended
- July 2026: recommended
- August 2026: not recommended
- September 2026: recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 6 people recommend itNeeds 10 or more, not met.
- Nobody criticizes itNeeds 2 to 1 or better, met.
- Recommended in 4 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Good introduction to Lean
“This is the best intro to Lean I know, plus it teaches you why a + b = b + a.”
Comment from 22 Jul 2026 in “Introduction to Formal Verification with Lean Part 1” “the excellent onboarding path that is the Natural Numbers Game”
Comment from 28 Apr 2026 in “"Why not just use Lean?"” “later picking up Lean by doing Natural Number Game”
Comment from 19 Sep 2026 in “I vibed a proof of Conway's conjecture” - Comment from 10 Jan 2026 in “AI solves Erdos problem #728 (Terence Tao mathstodon post)”
Recommended as a starting point
“later picking up Lean by doing Natural Number Game”
Comment from 19 Sep 2026 in “I vibed a proof of Conway's conjecture” “I'd recommend to check out the lean games”
Comment from 10 Jan 2026 in “AI solves Erdos problem #728 (Terence Tao mathstodon post)”
What people warn about
Each mark is one comment
Some tactics and semantics poorly explained
“some tactics and semantics weren't explained well enough that I could intuit how to use them”
Comment from 10 Sep 2026 in “Natural Number Game (Lean4 Tutorial)”
Other online tutorials people recommend
The four most recommended other online tutorials, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| CSS-Tricks | 23 | 3 | 88% | 4 | — | Approved |
| Beej's Guide to Network Programmingby Brian "beej Jorgensen" Hall | 16 | 1 | 94% | 7 | 23 yrs3 owners | Approved |
| Learn OpenGL | 15 | 3 | 83% | 3 | — | — |
| Let's Build a Compilerby Jack Crenshaw | 12 | 1 | 92% | 5 | — | Approved |
| Natural Number GameThis page | 6 | 0 | 100% | 4 | — | — |
What people said
6 of the 7 comments that mention it, newest first. Each links to the original comment.
“later picking up Lean by doing Natural Number Game”
“some tactics and semantics weren't explained well enough that I could intuit how to use them”
“The Natural Numbers Game is amazing, highly recommended.”
“This is the best intro to Lean I know, plus it teaches you why a + b = b + a.”
“the excellent onboarding path that is the Natural Numbers Game”
“I'd recommend to check out the lean games”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.