diff --git a/.babelrc b/.babelrc
index c13c5f6..002b4aa 100644
--- a/.babelrc
+++ b/.babelrc
@@ -1,3 +1,3 @@
 {
-  "presets": ["es2015"]
+  "presets": ["env"]
 }
diff --git a/package.json b/package.json
index d23afbd..95e0686 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,7 @@
     "regenerator-runtime": "^0.10.3"
   },
   "dependencies": {
-    "babel-preset-es2015": "^6.24.0",
+    "babel-preset-env": "^1.6.1",
     "eslint-config-airbnb": "^14.1.0"
   }
 }
diff --git a/src/arrays.js b/src/arrays.js
index b995952..f844408 100644
--- a/src/arrays.js
+++ b/src/arrays.js
@@ -5,35 +5,41 @@
 // You can use the functions that you have already written to help solve the other problems
 
 const each = (elements, cb) => {
+  // Reproduce the functionality of forEach from scratch.
   // Iterates over a list of elements, yielding each in turn to the `cb` function.
   // This only needs to work with arrays.
   // based off http://underscorejs.org/#each
 };
 
 const map = (elements, cb) => {
-  // Produces a new array of values by mapping each value in list through a transformation function (iteratee).
-  // Return the new array.
+  // Reproduce the functionality of map from scratch.
+  // Return a new array of values by mapping each value in a array through a transformation function (iteratee).
 };
 
 const reduce = (elements, cb, memo = elements.shift()) => {
+  // Reproduce the functionality of reduce from scratch.
   // Combine all elements into a single value going from left to right.
   // Elements will be passed one by one into `cb`.
   // `memo` is the starting value.  If `memo` is undefined then make `elements[0]` the initial value.
+  // Return the product of the callback.
 };
 
 const find = (elements, cb) => {
+  // Reproduce the functionality of find from scratch.
   // Look through each value in `elements` and pass each element to `cb`.
   // If `cb` returns `true` then return that element.
   // Return `undefined` if no elements pass the truth test.
 };
 
 const filter = (elements, cb) => {
+  // Reproduce the functionality of filter from scratch.
   // Similar to `find` but you will return an array of all elements that passed the truth test
   // Return an empty array if no elements pass the truth test
 };
 
 /* Extra Credit */
 const flatten = (elements) => {
+  // Reproduce the functionality of flatten from scratch.
   // Flattens a nested array (the nesting can be to any depth).
   // Example: flatten([1, [2], [3, [[4]]]]); => [1, 2, 3, 4];
 };
diff --git a/src/class.js b/src/class.js
index 8276e29..a58bfd3 100644
--- a/src/class.js
+++ b/src/class.js
@@ -14,7 +14,7 @@
 // `Cat` should extend the `Animal` class.
 // Animal and Cat should both have a parameter called `options` in their constructors.
 // Animal should have the property `age` that's set in the constructor and the method
-// `growOlder` that returns the age.
+// `growOlder` that returns the age incremented by one.
 // Cat should have the property `name` that is set in the constructor and the method
 // `meow` that should return the string `<name> meowed!` where `<name>` is the `name`
 // property set on the Cat instance.