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A MATHEMATICAL ADVENTURE FOR CURIOUS MINDS

A small why. A big adventure.

Follow the story. Try a proof. Let curiosity choose how deep you go.

No account. No API key. Just curiosity.

Two ways in. One table between them.

I'd rather not fight math today

Walk in through the manga: seventeen chapters, sixty-four pocket pebbles, zero required formulas. The Lean source stays behind glass until you ask for it.

Straight to the mathematics

Begin at the proof map — thousands of named theorems — then climb the full ladder from clock inverses to R = T. The story keeps telling itself beside you; it will keep you honest.

Made for company: one reader who loves math and one who does not — one sofa. Whatever each of you finds carries over to the tea salon.

Start with “I don’t know yet.”

Seventeen chapters, one extraordinary argument. One small discovery is enough for today.

17 chapters · LeanOriginal source ↗

Pip’s rule: mistakes are clues. Every chapter is open, and every question allows another try.

Modularity, the 3–5 trick, and compatible pieces.

Choose your depthProof terms and exact dependencies.
Explore the whole proof29,511 theorems · original statements · dependencies

Search the local catalogue in English or Japanese. Major landmarks have Japanese titles. Open the full original proof on GitHub for the complete context.

Your discovery in this chapter

See how a carefully chosen helper can solve a problem you cannot attack directly.

Existential witness
A concrete object together with proofs of its required properties.
exact_mod_cast
Close a goal after normalizing compatible numeric casts.
Where the metaphor ends

W′ is not equal to W. The theorem preserves particular mod-five information, not every property of the original curve.

</>S_WeierstrassCurve_threeFiveSwitchCurve.lean
Original source ↗ · L11–15Pinned revision aa2d8b3
theorem solution (W : WeierstrassCurve ℤ) (hΔ : W.Δ ≠ 0) (hW : W.IsSemistableModel) (h5 : W.ModRepIsIrreducible 5) : ∃ W' : WeierstrassCurve ℤ, W'.Δ ≠ 0 ∧ W'.IsSemistableModel ∧ W'.ModRepIsIrreducible 3 ∧ ∀ ℓ : ℕ, ℓ.Prime → W.IsGoodPrimeFor ℓ → W'.IsGoodPrimeFor ℓ → ℓ ≠ 5 → (5 : ℤ) ∣ (W'.apOfModel ℓ - W.apOfModel ℓ) := by
obtain ⟨W', hΔ', hW', h3', hφ⟩ := threeFiveAuxiliaryCurveExists W hΔ hW h5
refine ⟨W', hΔ', hW', h3', fun ℓ hℓ hℓW hℓW' hℓ5 => ?_⟩
exact_mod_cast
apOfModel_congr_of_torsionGaloisCongruent 5 Nat.prime_five W W' hΔ hΔ' hφ ℓ hℓ hℓW hℓW' hℓ5

👩🏻‍🎨 Mika · Source reading guide

threeFiveAuxiliaryCurveExists supplies W′, hΔ′, hW′, h3′ and hφ. refine returns these and a coefficient-congruence goal. apOfModel_congr_of_torsionGaloisCongruent supplies the needed divisibility, with exact_mod_cast adapting numeric casts. The prime-five irreducibility assumption is an explicit input.

Annotated original · not a live Lean state

Point to a story clue or a highlighted term to connect the two.

Try this logical move →
Source and verification details

Source: anthropics/fermats-last-theorem @ aa2d8b3. Upstream reports verification; this reader has not independently rebuilt the project. Manga explanations are not formal proofs.

Source license & attribution
Chapter 11/17 · Lean

Borrow a better passport

A second curve joins the cast. Pip requests a stunt double too.

How we got here

The direct modulo-3 route has conditions and may not apply. The 3–5 strategy introduces an auxiliary curve with matching residual information, so the argument can return through another entrance.

These links explain the reading route. A story analogy is not a proof of this theorem.

Take it to the tea salon
PIP
“Three is blocked. Bring in the yellow helper curve — not the lookalike, the one whose mod-three representation cannot split.”
A helpful double

Story → proofThe yellow helper is useful because its mod-three representation is irreducible. A lookalike alone cannot do the job.

A helper suitable for threeW'.ModRepIsIrreducible 3
MIKA
“An existence theorem hands over the helper. I did not assume it exists; the theorem did the vouching.”
Choose the right helper

Story → proofThe helper’s certificate is supplied by an existence theorem with conditions. Mika does not simply assume the helper is available.

A theorem supplies the helperthreeFiveAuxiliaryCurveExists

The idea behind the story

threeFiveAuxiliaryCurveExists supplies W′, hΔ′, hW′, h3′ and hφ. refine returns these and a coefficient-congruence goal. apOfModel_congr_of_torsionGaloisCongruent supplies the needed divisibility, with exact_mod_cast adapting numeric casts. The prime-five irreducibility assumption is an explicit input.

Which statement is a congruence modulo five?

  • 5 ∣ (aℓ(W′)−aℓ(W)).
  • aℓ(W′)=5 for all primes.

The story and source are readable here. Enable JavaScript to edit proofs, try quizzes, and explore the interactive map.

A matching fingerprint is promising. The lifting machinery explains why it can lead to full modularity.

Read. Try. Make it click.

  1. Read the manga and choose Story, Math, or Lean depth.
  2. Open the proof playground. Edit the tactics and watch the goals change.
  3. Select a state, term, or hint. Wrong turns are part of the story.

The playground checks a small propositional language. FLT excerpts are editable reading material, not live-checked Lean proofs. The complete FLT build remains an upstream verification report.

I’m lost · Help

Mika’s help desk

Borrow a better passport

One thing at a time

Start with the cake-scale story. You only need to read one small piece at a time. If you are in the Fermat story, start with Story depth, then the words listed before the chapter.

In simpler words

You do not need to know Lean, symbols or university mathematics to begin. Definitions come first in the small stories.

A small clue

Look at the small example before the general formula. Ask what changed and what stayed the same.

Close this panel to return to the exact place you were reading. These are prepared hints for this page.

Start with the first small story →