TITLE: LECTURE 3 — on pendulums
PROMPT: Create 'LECTURE 3 — on pendulums', a chalkboard lesson: a deep green-black board with chalk-dust texture where diagrams draw themselves in handwritten-style strokes (SVG dash animation with slight jitter for hand feel): a pendulum, formulas (T = 2π√(L/g)), a graph of period vs length. Beside the diagrams, a real working pendulum simulation demonstrates the lesson. Palette: chalk white, dust yellow, one pink chalk accent, wooden rail. Interactions: the ERASER clears board regions with a wipe and dust puff; dragging the pendulum bob and releasing it swings with true physics while a period timer chalks live readings; a length slider updates the drawn formula and graph together; tap the board to leave your own chalk dots. Scholarly, warm, hands-on.
DESCRIPTION: A green chalkboard in a wooden rail with dust grain and a chalk tray: Lecture III opens with a hand-drawn pendulum diagram (ceiling hatching, dashed swing positions, arc guide, italic L and θ labels, self-drawing via dash animation) beside the chalk formula T = 2π√(L/g) and professorial notes ("The clock doesn't care about the mass"). Below the diagram, a real working pendulum: drag the bob, release for true pendulum physics with a pink velocity arrow; zero-crossing detection chalks the measured period next to theory; the string-length slider rescales the swing and updates both readouts. The ERASER wipes the notes to a farewell line; tapping the board leaves pink chalk dots that fade; a length slider runs the whole demonstration.
TECHNIQUES: SVG dash-offset self-drawing diagram with hand-authored jitter, real pendulum integration with zero-crossing period measurement, drag-to-displace bob release, velocity arrow rendering, length-slider formula coupling, eraser choreography with notes swap, chalk-dot tap layer, board dust texture overlays.
INTERACTION: Drag the pendulum bob and let go; slide L; click the eraser to wipe the lecture; tap the board to chalk your own dots; compare measured vs theoretical period live.