03INSIDE A DEEP DECISION

FOLLOW
ONE POINT.

A deep network does not make one giant leap. It transforms the same point layer by layer, until the final cut becomes easy to make.

LIVE / FORWARD PASS

Move the point.
Trace the decision.

CLASS B93% CONFIDENCE
COMBINED DECISION SURFACEx = [72, 38]
THIS POINT → B

→ Click anywhere on the map or use the sliders. Every colored edge is a cut made by a hidden neuron.

04 / WHAT THE LAYERS DO

Each layer changes
the question.

LAYER 01

Find useful edges

Individual neurons make straight cuts: left or right, above or below, inside or outside.

LAYER 02

Combine regions

The next layer mixes those answers. Several half-spaces become corners, wedges, and bounded areas.

LAYER 03

Locate the point

The original coordinates have become a pattern of activations describing where the point belongs.

OUTPUT
B

Make the vote

The final neuron draws one last cut in the transformed space and returns the winning class.

The final cut is
still a cut.

The network’s apparent curve is made from many small straight boundaries. Earlier layers reshape the feature space; the output layer only needs to divide that reshaped space once.

score = w · h + b → probability → class
01

w says which hidden signals matter.

02

h is the point after all hidden transformations.

03

b positions the final decision threshold.

05 / THE ESSENTIAL INSIGHT

Deep means repeated re-description.

The network begins with raw coordinates. Each layer describes the same example in a more useful language: first edges, then regions, then shapes, then evidence for a class.

No neuron understands the whole decision. The intelligence is in the composition—simple cuts arranged so their combined boundary fits the data.

One point. Many cuts. One final decision.