<script src="http://spelprogrammering.nu/simple.js">
function start()
{
  A = {v: {x: 3,  y: -2}, x: 40,  y: 400, m: 1};
  B = {v: {x: -2, y: -3}, x: 420, y: 480, m: 1.5};
}

function update()
{
  fill("black");

  A.x += A.v.x;
  A.y += A.v.y;
  B.x += B.v.x;
  B.y += B.v.y;

  circle(A.x, A.y, 20, "red");
  circle(B.x, B.y, 20, "green");

  if (distance(A, B) < 40)
  {
    var normalVector = {x: A.x - B.x, y: A.y - B.y};
    var normalUV     = math.normalizeVector(normalVector);
    var tangentUV    = {x: -normalUV.y, y: normalUV.x};
  
    var AN = math.dotProduct(A.v, normalUV);
    var AT = math.dotProduct(A.v, tangentUV);
    var BN = math.dotProduct(B.v, normalUV);
    var BT = math.dotProduct(B.v, tangentUV);
  
    var newAN = (AN*(A.m - B.m) + 2*B.m*BN) / (A.m + B.m);
    var newBN = (BN*(B.m - A.m) + 2*A.m*AN) / (A.m + B.m);

    var vecAN = math.multiplyScalar(normalUV,  newAN);
    var vecAT = math.multiplyScalar(tangentUV, AT);
    var vecBN = math.multiplyScalar(normalUV,  newBN);
    var vecBT = math.multiplyScalar(tangentUV, BT);

    A.v = math.addVectors(vecAN, vecAT);
    B.v = math.addVectors(vecBN, vecBT);
  }
}
</script>