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Explainer

13 members

one concept × four levels × one stage system

What is this idea, at my level — and which part of the picture is which part of the formula?

CONCEPT EXPLAINER4 LEVELS · 5 STAGES

Neural Networks

Factory Workers

Passing little notes down the line

Imagine a room full of tiny workers holding strings. When a cat picture comes in, the first workers shout what they spot — pointy ears! whiskers! — and pass notes to the next row. The last row reads every note and yells the answer: cat! Each time they get it wrong, they swap a few strings around so the notes come out better next time.

It's a team game that gets sharper with every round.

Inside a single neuron

ŷ = σ(w₁x₁ + w₂x₂ + w₃x₃ + b)

Training progressAccuracyLoss
Accuracy rises and saturates while loss decays
E1E20E50E100E200
Architecture evolution

Perceptron

1958

~1K PARAMS

CNN

1989

~1M PARAMS

LSTM

1997

~10M PARAMS

Transformer

2017

10⁸–10¹² PARAMS

Parameter bars are log-scale — each step is roughly 1,000×

LEVEL: AGE 5

Members

each one a file and a roster line

Every member is admitted for its signature — the one thing the figure shows that the formula only says — and the roster prints it beside the name.

  1. 01Neural networksfive parts of one weighted sum

    The member the shell was extracted from: five stages bind a single neuron's figure, the four steps and the formula — click a step to trace it; the evidence is a training run, the ladder is four architecture eras on log-scale parameter counts.

  2. 02Attentionthe edge weight is the softmax weight

    One query reading four keys — edge weight IS the softmax weight, so the figure shows where the token looks before the steps say why. Evidence: heads sharpen as recall climbs over training; the ladder is context windows across four eras on a log scale.

  3. 03Gradient descentthe tangent is the gradient, the jump is the rate's share

    A ball three steps down a loss bowl: the tangent is the gradient, the horizontal jump is the learning rate's share of it, the dashed circle is where the update lands. Evidence: loss falls under a cosine schedule; the ladder is four optimizers by steps to converge on the same bowl.

  4. 04Bayes' theoremtwo positive boxes of the same area

    A thousand people as a frequency tree: 100 sick, 90 of them test positive — and so do 90 of the 900 well. The two positive boxes are the same size, which is the theorem's whole surprise drawn as area. Evidence: the posterior climbing with each further test; the ladder is base rates on a log scale.

  5. 05Compound interestthe third band is the only one that curves

    Eight yearly bars, each split into the principal, the interest it earned, and the interest that interest earned — the third band is the only one that curves. Evidence: compound against simple growth over forty years; the ladder is doubling time by rate.

  6. 06Fourier transforma shaded area becomes one bar

    Time on the left — a two-tone signal, the sinusoid it is tested against, their product with its area shaded — and frequency on the right, where that area becomes one bar. Evidence: a square wave's partial sums converging while the Gibbs overshoot refuses to; the ladder is sample rates on a log scale.

  7. 07TCP handshakeevery arrow's slope is a delay

    A sequence diagram of three messages — SYN, SYN-ACK, ACK — where every arrow's slope is a delay and the numbers on the arrows are the formula, so picture and formula are the same three facts. Evidence: slow start after the handshake; the ladder is one round trip across four distances.

  8. 08Entropyentropy is an area

    Entropy as area: one rectangle per symbol, width its probability and height its surprise, so every area is a contribution and the total is H — rare symbols tall and thin, common ones short and wide. Evidence: the binary entropy curve against Gini impurity; the ladder is bits per symbol from a coin to a byte.

  9. 09Central limit theoremthe parent stays skewed, the means become bells

    One skewed parent and, under it on the same axis, the bells that sample means make — wide for n = 4, narrow for n = 25, the means themselves as dots. The population never becomes normal; the averages do, and their spread is σ/√n. Evidence: the standard error falling with √n against the variance falling with n; the ladder is how far the noise drops for each sample size.

  10. 10PageRankevery circle's size is its rank

    A five-page web where every circle's size is its rank, computed by the power iteration the formula describes — links into a page, each linker's rank split across its out-links, a damping term that lets the surfer jump anywhere. Evidence: how many iterations the ranks take to settle at two dampings; the ladder is how far a surfer walks before jumping.

  11. 11Softmaxthe same four numbers, three times

    The same four logits three times: as signed bars, as exponentials that make every one positive and stretch the gaps, and as one stacked bar that adds to 100% — the negative class still gets a slice. Evidence: how the top probability and the entropy move with temperature; the ladder is how peaked the same logits become from icy to uniform.

  12. 12Likelihood ratiotwo tails past the same line

    Two bells — the well and the sick — cut by the same line: the sick's tail past it is the sensitivity, the well's is the false-positive rate, and their ratio is one number the test owns whatever the base rate. Evidence: the same ratio moving a low prior far less than a middling one; the ladder is how independent results stack on a log scale.

  13. 13Law of large numbersthree wandering means narrow into one line

    Three running means of a die, wild for the first rolls and narrowing into the line at 3.5 as n grows, with the ±0.5 band they enter and stay in — the single rolls never settle, their average does. The Central Limit Theorem's pair: that one says what shape the means take, this one says where they go. Evidence: how often a run is still outside the band at each n; the ladder is the rolls it takes to pin the mean to a tolerance.

What makes a member

A concept that has a formula with named parts and a picture of those parts. The member declares its stages; the shell binds each stage's hue to the figure, the numbered steps and the formula tokens, so clicking a step traces it through all three. Four fixed rungs of copy (Age 5 → PhD), one evidence chart, one scale ladder. Not for a procedure with no formula (that is a Lineage diagram) or a comparison (Versus).

A member supplies stages · four rungs of copy · steps and formula tokens keyed to stages · a sampled evidence chart · a log-scale ladder · one custom figure · adding one is a file and a roster line