Energy and damage

math.js

@@ -27,6 +27,10 @@ export function wrap(min, x, max) {
   return ((x-min + max-min) % (max-min)) + min;
 }
 
+export function within(x, y, tx, ty, r) {
+  return Math.abs(x-tx) < r && Math.abs(y-ty) < r;
+}
+
 export function parable(t, x, y, a, v, w=0, g=9.8) {
   const fx = x + t*v * Math.cos(a) - 0.5 * -w * t*t;
   const fy = y + t*v * Math.sin(a) - 0.5 * -g * t*t;