Processing-style sketching in Odin for pen plotting. Sketches draw through a small immediate-mode canvas API, raylib shows a live preview, and a keypress exports the frame as a minimal SVG ready for the hpgl_plot pipeline (svg2hpgl.py -> HP 7440A).

odin run sketches/demo -out:build/demo

In the preview window:

• S — export the current frame to svg/plot_<timestamp>.svg
• R — reroll the random seed (sketches are deterministic per seed)
• Esc — quit

New sketch: copy sketches/template/, rename the package, edit draw.

All procs take the canvas first: plot.line(c, x1, y1, x2, y2).

• Shapes: line, point, circle, ellipse, rect, bezier
• Free-form: begin_shape / vertex / end_shape(close = ...)
• Transforms: push_matrix, pop_matrix, translate, rotate, scale
• pen(c, n) — select carousel pen 1-8 for subsequent shapes (color-coded in the preview)
• stroke_weight — preview line width, recorded per shape and written as SVG stroke-width

Transforms are baked into coordinates when a shape is recorded, and curves are flattened to polylines, so exports stay within the element subset svg2hpgl.py understands: line, circle, polyline, polygon with strokes only.

Each pen's shapes export as their own <g data-pen="n" stroke="..."> group in one shared SVG, so per-pen plotting keeps registration (the converter's fit is computed from the whole drawing). svg2hpgl.py currently plots everything with its single configured pen; filtering by data-pen is a converter-side change.