Bézier Curve Editor — Animated De Casteljau Construction (2D)

This is the 2D companion to the 3D Bézier Curves simulator. It renders the same De Casteljau algorithm on a plain 2D canvas instead of through WebGL, and adds a step-by-step construction build-up: instead of drawing every interpolation level at once, pressing Step Construction replays the recursive linear interpolation one level at a time, animating each new line as it grows into place. Drag the control points to reshape either a quadratic or a cubic curve, scrub the t slider to move the point-at-t marker, and watch how each round of interpolation feeds the next until a single point on the curve remains.