This page is interactive and requires JavaScript. The construction tools, mode switching, dependency graphs, and proof reconstruction all run in the browser. The non-interactive shape of each proposition — its statement, postulates, and proof structure — is available in the propositions reference and the foundations page.

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Free construction · choose a tool

Tool — Straight line Click a point. Then click a second, distinct point, to draw the segment between them.

Goals

Construction closed

After the reveal

Now reproduce this on paper, by hand, without looking. Compass and straightedge only — no ruler, no measurements. We'll surface the prompt again in 24h.

Construction history

No moves yet. Pick a tool below and act.

Tutor → 0 / 0 goals

Tutor —

What this proof rests on

The minimal foundation this proposition actually depends on.

→ Browse all foundations

The figure and the proof are hidden. Rebuild the argument in your own words — naming each move and the postulate, definition, or prior proposition that licenses it. Your attempt is saved to the practice queue and brought back at increasing intervals.

Practice queue →