Click with the Point tool to place a free point (or drag an existing one), then Line/Circle to connect existing points. Each Line/Circle also gets a genuinely dependent length/radius cell reading its points' live coordinates — the Objects list below shows both kinds side by side. Reflect/Rotate/Translate each construct a new point that is itself dependent on the point(s) it was built from, so dragging a free point cascades through every line, circle, and transform built from it. Free points are drawn in blue, dependent (constructed) points in gray-blue — only free points are draggable, since a dependent point's position is entirely determined by what it was built from. A Line/Circle whose defining points have collapsed onto each other (zero length/radius) draws in amber instead — the same declarative condition-flag pattern /multi uses for root crossings and discontinuities, applied here to "this construction has degenerated." Scale dilates a point about a center by a fixed factor; Angle measures the interior angle between two rays (click a point, the vertex, then the other point); Polygon connects an ordered run of vertices, closed by re-clicking the first one, with its area shown in the Objects list.
Click empty space to place a point, or drag an existing one.