diff --git a/shapes.js b/shapes.js
index 20df403..9288fc4 100644
--- a/shapes.js
+++ b/shapes.js
@@ -9,6 +9,12 @@ class Rectangle {
   }
 }
 
+class CircleGetsTheSquare {
+  constructor(circumference, radius) {
+    this.circumference = circumference
+    this.radius = radius
+  }
+
 class Square extends Rectangle {
   constructor(x) {
     super(x, x)
diff --git a/underscore.js b/underscore.js
index 014ebfa..170e2d3 100644
--- a/underscore.js
+++ b/underscore.js
@@ -27,6 +27,24 @@ _.min = function(obj, iteratee, context) {
 	return result;
 };
 
+_.sampleThis = function(obj, n, guard) {
+	if (n == null || guard) {
+		if (!isArrayLike(obj)) obj = _.values(obj);
+		return obj[_.random(obj.length - 1)];
+	}
+	var sample = isArrayLike(obj) ? _.clone(obj) : _.values(obj);
+	var length = getLength(sample);
+	n = Math.max(Math.min(n, length), 0);
+	var last = length - 1;
+	for (var index = 0; index < n; index++) {
+		var rand = _.random(index, last);
+		var temp = sample[index];
+		sample[index] = sample[rand];
+		sample[rand] = temp;
+	}
+	return sample.slice(0, n);
+};
+
 _.shuffle = function(obj) {
 	return _.sample(obj, Infinity);
 };