diagonal rungs are drawing. just need tranches.

src/vector.js

@@ -41,6 +41,11 @@ export function vectorEquals(a, b) {
 }
 
 
+export function vectorNeg(a) {
+    return a.map((v)=>-v)
+}
+
+
 export function vectorAdd(a, b) {
     const result = []
     const scalarB = b.length === undefined