Costing and feel-related movement fixes

src/engine/datatypes.ts

@@ -105,6 +105,12 @@ export class Point {
       lerp(y, Math.floor(this.y), Math.ceil(this.y)),
     );
   }
+
+  distance(other: Point) {
+    let dx = other.x - this.x;
+    let dy = other.y - this.y;
+    return Math.sqrt(dx * dx + dy * dy);
+  }
 }
 
 export class Size {