diff --git a/Makefile b/Makefile
index 9a1cbf30a4..de2a259761 100644
--- a/Makefile
+++ b/Makefile
@@ -92,7 +92,7 @@ publish:
 	make publish-core
 	make publish-runtime
 
-	rm -rf templates.json browser.js browser-polyfill.js
+	rm -rf templates.json browser.js browser-polyfill.js runtime.js
 
 publish-runtime:
 	cd packages; \
diff --git a/bin/6to5/util.js b/bin/6to5/util.js
index bd196c8fa0..7cfcbb70ce 100644
--- a/bin/6to5/util.js
+++ b/bin/6to5/util.js
@@ -2,7 +2,7 @@ var readdir = require("fs-readdir-recursive");
 var index   = require("./index");
 var util    = require("../../lib/6to5/util");
 var path    = require("path");
-var to5     = require("../../lib/6to5");
+var to5     = require("../../lib/6to5/api/node");
 var fs      = require("fs");
 var _       = require("lodash");
 
diff --git a/bin/_6to5-node b/bin/_6to5-node
index d35558a5aa..982ed5dbc9 100644
--- a/bin/_6to5-node
+++ b/bin/_6to5-node
@@ -4,7 +4,7 @@ var commander = require("commander");
 var Module    = require("module");
 var path      = require("path");
 var repl      = require("repl");
-var to5       = require("../lib/6to5");
+var to5       = require("../lib/6to5/api/node");
 var util      = require("../lib/6to5/util");
 var vm        = require("vm");
 var _         = require("lodash");
diff --git a/lib/6to5/browser.js b/lib/6to5/api/browser.js
similarity index 94%
rename from lib/6to5/browser.js
rename to lib/6to5/api/browser.js
index 9f0d32b425..2de894e56f 100644
--- a/lib/6to5/browser.js
+++ b/lib/6to5/api/browser.js
@@ -1,8 +1,8 @@
 "use strict";
 
-var transform = module.exports = require("./transformation");
+var transform = module.exports = require("../transformation");
 
-transform.version = require("../../package").version;
+transform.version = require("../../../package").version;
 
 transform.transform = transform;
 
diff --git a/lib/6to5/index.js b/lib/6to5/api/node.js
similarity index 76%
rename from lib/6to5/index.js
rename to lib/6to5/api/node.js
index de4474c5d4..fbe3843d9e 100644
--- a/lib/6to5/index.js
+++ b/lib/6to5/api/node.js
@@ -1,24 +1,24 @@
 "use strict";
 
-var transform  = require("./transformation");
-var util       = require("./util");
-var fs         = require("fs");
 var isFunction = require("lodash/lang/isFunction");
+var transform  = require("../transformation");
+var util       = require("../util");
+var fs         = require("fs");
 
-exports.version = require("../../package").version;
+exports.version = require("../../../package").version;
 
-exports.runtime = require("./build-runtime");
+exports.runtime = require("../build-runtime");
 
-exports.types = require("./types");
+exports.types = require("../types");
 
 exports.register = function (opts) {
-  var register = require("./register");
+  var register = require("./register/node");
   if (opts != null) register(opts);
   return register;
 };
 
 exports.polyfill = function () {
-  require("./polyfill");
+  require("../polyfill");
 };
 
 exports.canCompile = util.canCompile;
diff --git a/lib/6to5/register-browser.js b/lib/6to5/api/register/browser.js
similarity index 81%
rename from lib/6to5/register-browser.js
rename to lib/6to5/api/register/browser.js
index bd18a5fbc9..f7576c91ac 100644
--- a/lib/6to5/register-browser.js
+++ b/lib/6to5/api/register/browser.js
@@ -4,4 +4,4 @@
 
 module.exports = function () {};
 
-require("./polyfill");
+require("../../polyfill");
diff --git a/lib/6to5/register-cache.js b/lib/6to5/api/register/cache.js
similarity index 100%
rename from lib/6to5/register-cache.js
rename to lib/6to5/api/register/cache.js
diff --git a/lib/6to5/register.js b/lib/6to5/api/register/node.js
similarity index 95%
rename from lib/6to5/register.js
rename to lib/6to5/api/register/node.js
index 68f40886fd..f4837a4276 100644
--- a/lib/6to5/register.js
+++ b/lib/6to5/api/register/node.js
@@ -1,14 +1,14 @@
 "use strict";
 
-require("./polyfill");
+require("../../polyfill");
 
 var sourceMapSupport = require("source-map-support");
-var registerCache    = require("./register-cache");
-var util             = require("./util");
-var to5              = require("./index");
-var fs               = require("fs");
+var registerCache    = require("./cache");
 var extend           = require("lodash/object/extend");
 var each             = require("lodash/collection/each");
+var util             = require("../../util");
+var to5              = require("../node");
+var fs               = require("fs");
 
 sourceMapSupport.install({
   retrieveSourceMap: function (source) {
diff --git a/lib/6to5/build-helpers.js b/lib/6to5/build-helpers.js
index f9640abd27..82b3975517 100644
--- a/lib/6to5/build-helpers.js
+++ b/lib/6to5/build-helpers.js
@@ -1,4 +1,4 @@
-var File = require("./file");
+var File = require("./transformation/file");
 var util = require("./util");
 var each = require("lodash/collection/each");
 var t    = require("./types");
diff --git a/lib/6to5/detection/index.js b/lib/6to5/detection/index.js
index 942342a8ad..7d2eb54c86 100644
--- a/lib/6to5/detection/index.js
+++ b/lib/6to5/detection/index.js
@@ -1,7 +1,7 @@
 module.exports = detect;
 
 var SYNTAX_KEYS = require("./syntax-keys");
-var traverse    = require("../traverse");
+var traverse    = require("../traversal");
 var visitors    = traverse.explode(require("./visitors"));
 
 function detect(ast) {
diff --git a/lib/6to5/helpers/normalize-ast.js b/lib/6to5/helpers/normalize-ast.js
new file mode 100644
index 0000000000..54631556c9
--- /dev/null
+++ b/lib/6to5/helpers/normalize-ast.js
@@ -0,0 +1,9 @@
+var t = require("../types");
+
+module.exports = function (ast, comments, tokens) {
+  if (ast && ast.type === "Program") {
+    return t.file(ast, comments || [], tokens || []);
+  } else {
+    throw new Error("Not a valid ast?");
+  }
+};
diff --git a/lib/6to5/helpers/parse.js b/lib/6to5/helpers/parse.js
new file mode 100644
index 0000000000..1b2a9a8fca
--- /dev/null
+++ b/lib/6to5/helpers/parse.js
@@ -0,0 +1,49 @@
+var normalizeAst = require("./normalize-ast");
+var estraverse   = require("estraverse");
+var codeFrame    = require("./code-frame");
+var acorn        = require("acorn-6to5");
+
+module.exports = function (opts, code, callback) {
+  try {
+    var comments = [];
+    var tokens   = [];
+
+    var ast = acorn.parse(code, {
+      allowImportExportEverywhere: opts.allowImportExportEverywhere,
+      allowReturnOutsideFunction:  !opts._anal,
+      ecmaVersion:                 opts.experimental ? 7 : 6,
+      playground:                  opts.playground,
+      strictMode:                  opts.strictMode,
+      onComment:                   comments,
+      locations:                   true,
+      onToken:                     tokens,
+      ranges:                      true
+    });
+
+    estraverse.attachComments(ast, comments, tokens);
+
+    ast = normalizeAst(ast, comments, tokens);
+
+    if (callback) {
+      return callback(ast);
+    } else {
+      return ast;
+    }
+  } catch (err) {
+    if (!err._6to5) {
+      err._6to5 = true;
+      var message = opts.filename + ": " + err.message;
+
+      var loc = err.loc;
+      if (loc) {
+        var frame = codeFrame(code, loc.line, loc.column + 1);
+        message += frame;
+      }
+
+      if (err.stack) err.stack = err.stack.replace(err.message, message);
+      err.message = message;
+    }
+
+    throw err;
+  }
+};
diff --git a/lib/6to5/patch.js b/lib/6to5/patch.js
index adda701345..7a3d9a7081 100644
--- a/lib/6to5/patch.js
+++ b/lib/6to5/patch.js
@@ -1,7 +1,7 @@
 "use strict";
 
-var t      = require("./types");
 var extend = require("lodash/object/extend");
+var t      = require("./types");
 
 require("./types/node");
 
diff --git a/lib/6to5/file.js b/lib/6to5/transformation/file.js
similarity index 94%
rename from lib/6to5/file.js
rename to lib/6to5/transformation/file.js
index 7d5cc035d2..75a1cb0ddc 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/transformation/file.js
@@ -5,16 +5,17 @@ module.exports = File;
 var SHEBANG_REGEX = /^\#\!.*/;
 
 var isFunction = require("lodash/lang/isFunction");
-var transform  = require("./transformation");
-var generate   = require("./generation");
+var transform  = require("./index");
+var generate   = require("../generation");
 var defaults   = require("lodash/object/defaults");
 var contains   = require("lodash/collection/contains");
-var clone      = require("./helpers/clone");
-var Scope      = require("./traverse/scope");
-var util       = require("./util");
+var clone      = require("../helpers/clone");
+var parse      = require("../helpers/parse");
+var Scope      = require("../traversal/scope");
+var util       = require("../util");
 var path       = require("path");
 var each       = require("lodash/collection/each");
-var t          = require("./types");
+var t          = require("../types");
 
 function File(opts) {
   this.dynamicImportIds = {};
@@ -334,7 +335,7 @@ File.prototype.parse = function (code) {
   opts.allowImportExportEverywhere = this.isLoose("es6.modules");
   //opts.strictMode = this.transformers.useStrict.canRun();
 
-  return util.parse(opts, code, function (tree) {
+  return parse(opts, code, function (tree) {
     self.transform(tree);
     return self.generate();
   });
@@ -373,25 +374,25 @@ File.prototype.transform = function (ast) {
 
 var checkTransformerVisitor = {
   enter: function (node, parent, scope, context, state) {
-    state.check(node, scope);
+    checkNode(state.stack, node, scope);
   }
 };
 
+var checkNode = function (stack, node, scope) {
+  each(stack, function (pass) {
+    if (pass.shouldRun) return;
+    pass.checkNode(node, scope);
+  });
+};
+
 File.prototype.checkNode = function (node, scope) {
-  var self = this;
+  var stack = this.transformerStack;
   scope = scope || this.scope;
 
-  var check = function (node, scope) {
-    each(self.transformerStack, function (pass) {
-      if (pass.shouldRun) return;
-      pass.checkNode(node, scope);
-    });
-  };
-
-  check(node, scope);
+  checkNode(stack, node, scope);
 
   scope.traverse(node, checkTransformerVisitor, {
-    check: check
+    stack: stack
   });
 };
 
diff --git a/lib/6to5/transformation/helpers/define-map.js b/lib/6to5/transformation/helpers/define-map.js
index b463e9045e..cd7f82b0f1 100644
--- a/lib/6to5/transformation/helpers/define-map.js
+++ b/lib/6to5/transformation/helpers/define-map.js
@@ -1,5 +1,5 @@
 var cloneDeep = require("lodash/lang/cloneDeep");
-var traverse  = require("../../traverse");
+var traverse  = require("../../traversal");
 var clone      = require("lodash/lang/clone");
 var each      = require("lodash/collection/each");
 var has       = require("lodash/object/has");
diff --git a/lib/6to5/transformation/index.js b/lib/6to5/transformation/index.js
index eec84eae40..755b5f5a8b 100644
--- a/lib/6to5/transformation/index.js
+++ b/lib/6to5/transformation/index.js
@@ -2,11 +2,12 @@
 
 module.exports = transform;
 
-var Transformer = require("./transformer");
-var object      = require("../helpers/object");
-var File        = require("../file");
-var util        = require("../util");
-var each        = require("lodash/collection/each");
+var normalizeAst = require("../helpers/normalize-ast");
+var Transformer  = require("./transformer");
+var object       = require("../helpers/object");
+var File         = require("./file");
+var util         = require("../util");
+var each         = require("lodash/collection/each");
 
 function transform(code, opts) {
   var file = new File(opts);
@@ -14,7 +15,7 @@ function transform(code, opts) {
 }
 
 transform.fromAst = function (ast, code, opts) {
-  ast = util.normalizeAst(ast);
+  ast = normalizeAst(ast);
 
   var file = new File(opts);
   file.addCode(code);
diff --git a/lib/6to5/transformation/transformer.js b/lib/6to5/transformation/transformer.js
index ce4a87e3d9..2f94ff3f69 100644
--- a/lib/6to5/transformation/transformer.js
+++ b/lib/6to5/transformation/transformer.js
@@ -4,7 +4,7 @@ module.exports = Transformer;
 
 var TransformerPass = require("./transformer-pass");
 var isFunction      = require("lodash/lang/isFunction");
-var traverse        = require("../traverse");
+var traverse        = require("../traversal");
 var isObject        = require("lodash/lang/isObject");
 var each            = require("lodash/collection/each");
 
diff --git a/lib/6to5/transformation/transformers/es6/block-scoping.js b/lib/6to5/transformation/transformers/es6/block-scoping.js
index 8a1c7775b3..2a6edc14fd 100644
--- a/lib/6to5/transformation/transformers/es6/block-scoping.js
+++ b/lib/6to5/transformation/transformers/es6/block-scoping.js
@@ -1,6 +1,6 @@
 "use strict";
 
-var traverse = require("../../../traverse");
+var traverse = require("../../../traversal");
 var object   = require("../../../helpers/object");
 var util     = require("../../../util");
 var t        = require("../../../types");
diff --git a/lib/6to5/transformation/transformers/es7/comprehensions.js b/lib/6to5/transformation/transformers/es7/comprehensions.js
index 9b9a4d2b9c..a7b613ce69 100644
--- a/lib/6to5/transformation/transformers/es7/comprehensions.js
+++ b/lib/6to5/transformation/transformers/es7/comprehensions.js
@@ -1,7 +1,7 @@
 "use strict";
 
 var buildComprehension = require("../../helpers/build-comprehension");
-var traverse           = require("../../../traverse");
+var traverse           = require("../../../traversal");
 var util               = require("../../../util");
 var t                  = require("../../../types");
 
diff --git a/lib/6to5/transformation/transformers/minification/dead-code-elimination.js b/lib/6to5/transformation/transformers/minification/dead-code-elimination.js
index 0d92cddb4e..5668829823 100644
--- a/lib/6to5/transformation/transformers/minification/dead-code-elimination.js
+++ b/lib/6to5/transformation/transformers/minification/dead-code-elimination.js
@@ -25,7 +25,7 @@ exports.IfStatement = {
     var alternate  = node.alternate;
     var test       = node.test;
 
-    // we can check if a test will be truthy 100% and if so we can inline
+    // we can check if a test will be truthy 100% and if so then we can inline
     // the consequent and completely ignore the alternate
     //
     //   if (true) { foo; } -> { foo; }
@@ -36,8 +36,8 @@ exports.IfStatement = {
       return alternate;
     }
 
-    // we can check if a test will be falsy 100% and if so we can inline
-    // the alternate if there is one and completely remove the consequent
+    // we can check if a test will be falsy 100% and if so we can inline the
+    // alternate if there is one and completely remove the consequent
     //
     //   if ("") { bar; } else { foo; } -> { foo; }
     //   if ("") { bar; } ->
@@ -60,11 +60,10 @@ exports.IfStatement = {
       alternate = node.alternate = null;
     }
 
-    // turn alternate blocks into a consequent and flip the test if the
-    // consequent block is empty
+    // if the consequent block is empty turn alternate blocks into a consequent
+    // and flip the test
     //
-    //   if (foo) {} else { bar; }
-    //   if (!foo) { bar; }
+    //   if (foo) {} else { bar; } -> if (!foo) { bar; }
     //
 
     if (t.blockStatement(consequent) && !consequent.body.length &&
diff --git a/lib/6to5/transformation/transformers/playground/object-getter-memoization.js b/lib/6to5/transformation/transformers/playground/object-getter-memoization.js
index 12458e3702..5f49b46dc2 100644
--- a/lib/6to5/transformation/transformers/playground/object-getter-memoization.js
+++ b/lib/6to5/transformation/transformers/playground/object-getter-memoization.js
@@ -6,7 +6,7 @@ exports.playground = true;
 
 var visitor = {
   enter: function (node, parent, scope, context, state) {
-    if (t.isFunction(node)) return;
+    if (t.isFunction(node)) return context.skip();
 
     if (t.isReturnStatement(node) && node.argument) {
       node.argument = t.memberExpression(t.callExpression(state.file.addHelper("define-property"), [
@@ -22,7 +22,6 @@ exports.Property =
 exports.MethodDefinition = function (node, parent, scope, context, file) {
   if (node.kind !== "memo") return;
   node.kind = "get";
-  file.checkNode(node, scope);
 
   var value = node.value;
   t.ensureBlock(value);
@@ -39,4 +38,6 @@ exports.MethodDefinition = function (node, parent, scope, context, file) {
   };
 
   scope.traverse(value, visitor, state);
+
+  return node;
 };
diff --git a/lib/6to5/traverse/index.js b/lib/6to5/traversal/index.js
similarity index 100%
rename from lib/6to5/traverse/index.js
rename to lib/6to5/traversal/index.js
diff --git a/lib/6to5/traverse/scope.js b/lib/6to5/traversal/scope.js
similarity index 98%
rename from lib/6to5/traverse/scope.js
rename to lib/6to5/traversal/scope.js
index f4639fd6ac..064aae2290 100644
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traversal/scope.js
@@ -341,8 +341,6 @@ Scope.prototype.crawl = function () {
 
   if (t.isFunctionExpression(block) && block.id) {
     if (!t.isProperty(this.parentBlock, { method: true })) {
-      // SpiderMonkey AST doesn't use MethodDefinition here when it probably
-      // should since they should be semantically the same?
       this.register(block.id);
     }
   }
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index 8cf3aa3fd7..756c76292c 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -2,23 +2,22 @@
 
 require("./patch");
 
-var estraverse = require("estraverse");
+var cloneDeep  = require("lodash/lang/cloneDeep");
 var codeFrame  = require("./helpers/code-frame");
-var traverse   = require("./traverse");
-var debug      = require("debug/node");
-var acorn      = require("acorn-6to5");
-var path       = require("path");
-var util       = require("util");
-var fs         = require("fs");
-var t          = require("./types");
-var each       = require("lodash/collection/each");
+var contains   = require("lodash/collection/contains");
+var traverse   = require("./traversal");
 var isNumber   = require("lodash/lang/isNumber");
 var isString   = require("lodash/lang/isString");
 var isRegExp   = require("lodash/lang/isRegExp");
 var isEmpty    = require("lodash/lang/isEmpty");
-var cloneDeep  = require("lodash/lang/cloneDeep");
+var parse      = require("./helpers/parse");
+var debug      = require("debug/node");
+var path       = require("path");
+var util       = require("util");
+var each       = require("lodash/collection/each");
 var has        = require("lodash/object/has");
-var contains   = require("lodash/collection/contains");
+var fs         = require("fs");
+var t          = require("./types");
 
 exports.inherits = util.inherits;
 
@@ -123,61 +122,8 @@ exports.repeat = function (width, cha) {
   return result;
 };
 
-exports.normalizeAst = function (ast, comments, tokens) {
-  if (ast && ast.type === "Program") {
-    return t.file(ast, comments || [], tokens || []);
-  } else {
-    throw new Error("Not a valid ast?");
-  }
-};
-
-exports.parse = function (opts, code, callback) {
-  try {
-    var comments = [];
-    var tokens   = [];
-
-    var ast = acorn.parse(code, {
-      allowImportExportEverywhere: opts.allowImportExportEverywhere,
-      allowReturnOutsideFunction:  !opts._anal,
-      ecmaVersion:                 opts.experimental ? 7 : 6,
-      playground:                  opts.playground,
-      strictMode:                  opts.strictMode,
-      onComment:                   comments,
-      locations:                   true,
-      onToken:                     tokens,
-      ranges:                      true
-    });
-
-    estraverse.attachComments(ast, comments, tokens);
-
-    ast = exports.normalizeAst(ast, comments, tokens);
-
-    if (callback) {
-      return callback(ast);
-    } else {
-      return ast;
-    }
-  } catch (err) {
-    if (!err._6to5) {
-      err._6to5 = true;
-      var message = opts.filename + ": " + err.message;
-
-      var loc = err.loc;
-      if (loc) {
-        var frame = codeFrame(code, loc.line, loc.column + 1);
-        message += frame;
-      }
-
-      if (err.stack) err.stack = err.stack.replace(err.message, message);
-      err.message = message;
-    }
-
-    throw err;
-  }
-};
-
 exports.parseTemplate = function (loc, code) {
-  var ast = exports.parse({ filename: loc }, code).program;
+  var ast = parse({ filename: loc }, code).program;
   return traverse.removeProperties(ast);
 };
 
diff --git a/package.json b/package.json
index 0f603c6358..13787b1e9f 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,8 @@
   "homepage": "https://6to5.org/",
   "repository": "6to5/6to5",
   "preferGlobal": true,
-  "main": "lib/6to5/index.js",
+  "main": "lib/6to5/api/node.js",
+  "browser": "lib/6to5/api/browser.js",
   "bin": {
     "6to5": "./bin/6to5/index.js",
     "6to5-minify": "./bin/6to5-minify",
@@ -14,8 +15,7 @@
     "6to5-runtime": "./bin/6to5-runtime"
   },
   "browser": {
-    "./lib/6to5/index.js": "./lib/6to5/browser.js",
-    "./lib/6to5/register.js": "./lib/6to5/register-browser.js"
+    "./lib/6to5/api/register/node.js": "./lib/6to5/api/register/browser.js"
   },
   "keywords": [
     "harmony",
diff --git a/packages/6to5-runtime/package.json b/packages/6to5-runtime/package.json
index f91a1b6798..e1fe7e15b6 100644
--- a/packages/6to5-runtime/package.json
+++ b/packages/6to5-runtime/package.json
@@ -1,7 +1,7 @@
 {
   "name": "6to5-runtime",
   "description": "6to5 selfContained runtime",
-  "version": "3.3.11",
+  "version": "3.3.12",
   "repository": "6to5/6to5",
   "author": "Sebastian McKenzie <sebmck@gmail.com>"
 }
\ No newline at end of file
diff --git a/register.js b/register.js
index a8de654c4b..51f2ac517b 100644
--- a/register.js
+++ b/register.js
@@ -1 +1 @@
-module.exports = require("./lib/6to5/register");
+module.exports = require("./lib/6to5/api/register/node");
diff --git a/test/detection.js b/test/detection.js
index 781b17caeb..1b237b2620 100644
--- a/test/detection.js
+++ b/test/detection.js
@@ -1,10 +1,10 @@
 var detect = require("../lib/6to5/detection");
 var assert = require("assert");
-var util   = require("../lib/6to5/util");
+var parse  = require("../lib/6to5/helpers/parse");
 
 suite("detection", function () {
   var checkSyntax = function (code, name) {
-    var ast = util.parse({
+    var ast = parse({
       experimental: true
     }, code);
 
diff --git a/test/generation.js b/test/generation.js
index ba7c22efa9..e24d1e3e5a 100644
--- a/test/generation.js
+++ b/test/generation.js
@@ -1,7 +1,7 @@
 var generate = require("../lib/6to5/generation");
 var assert   = require("assert");
 var helper   = require("./_helper");
-var util     = require("../lib/6to5/util");
+var parse    = require("../lib/6to5/helpers/parse");
 var chai     = require("chai");
 var t        = require("../lib/6to5/types");
 var _        = require("lodash");
@@ -26,7 +26,7 @@ _.each(helper.get("generation"), function (testSuite) {
         var expect = task.expect;
         var actual = task.actual;
 
-        var actualAst  = util.parse({ filename: actual.loc, experimental: true }, actual.code);
+        var actualAst  = parse({ filename: actual.loc, experimental: true }, actual.code);
         var actualCode = generate(actualAst, null, actual.code).code;
 
         chai.expect(actualCode).to.equal(expect.code, actual.loc + " !== " + expect.loc);