Improve zigzaging

src/main.ts

@@ -1,4 +1,4 @@
-import { line, type Line, group, translate, asSvg, svgDoc, scale } from "@thi.ng/geom";
+import { line, type Line, group, translate, asSvg, svgDoc, scale, flip } from "@thi.ng/geom";
 import { vec2, type Vec2 } from "@thi.ng/vectors"
 import { $canvas } from "@thi.ng/rdom-canvas";
 import { reactive, sync } from "@thi.ng/rstream";
@@ -66,15 +66,11 @@ const generateLines = (maxCoordOnAxis: number, maxCoordPerpendicular: number, se
   iterator(
     comp(
       map(([coord, seed]) => [coord, stitches(seed, maxCoordPerpendicular)] as const),
-      // optimization for quicker drawing: when we're in an odd row / col,
-      // reverse drawing direction
-      mapcat(([coord, stitches]) =>
-        map(
-          l => lineGen(coord, l),
-          coord % 2 === 0
-            ? stitches
-            : reverse(map(([p1, p2]) => vec2(p2, p1), stitches))
-        )
+      // optimization for faster drawing: alternate drawing directions to
+      // minimize pen movements
+      mapcat(([coord, stitches]) => coord % 2 === 0
+        ? map(l => lineGen(coord, l), stitches)
+        : map(l => flip(lineGen(coord, l)), reverse(stitches))
       )
     ),
     zip(range(maxCoordOnAxis + 1), seeds)