prevent -0

src/point.js

@@ -1,8 +1,9 @@
 
 export default class Point {
 	constructor(x, y) {
-		this.x = Math.round(x);
-		this.y = Math.round(y);
+		// add zero to turn -0 into 0
+		this.x = Math.round(x) + 0;
+		this.y = Math.round(y) + 0;
 	}
 
 	getX() { return this.x; }