diff --git a/bin/6to5/index.js b/bin/6to5/index.js
index d79fe08162..a1c88877ba 100755
--- a/bin/6to5/index.js
+++ b/bin/6to5/index.js
@@ -12,6 +12,7 @@ commander.option("-f, --filename [filename]", "Filename to use when reading from
 commander.option("-w, --watch", "Recompile files on changes");
 commander.option("-r, --runtime", "Replace 6to5 declarations with references to a runtime");
 commander.option("-e, --experimental", "Enable experimental support for proposed ES7 features");
+commander.option("-p, --playground", "Enable playground support");
 
 commander.option("-m, --modules [modules]", "Module formatter type to use [common]", "common");
 commander.option("-w, --whitelist [whitelist]", "Whitelist of transformers to ONLY use", util.list);
@@ -90,6 +91,7 @@ exports.opts = {
   sourceMapName: commander.outFile,
   amdModuleIds:  commander.amdModuleIds,
   experimental:  commander.experimental,
+  playground:    commander.playground,
   blacklist:     commander.blacklist,
   whitelist:     commander.whitelist,
   sourceMap:     commander.sourceMaps || commander.sourceMapsInline,
diff --git a/bin/_6to5-node b/bin/_6to5-node
index dd7216d35a..62d30b0512 100644
--- a/bin/_6to5-node
+++ b/bin/_6to5-node
@@ -13,6 +13,7 @@ commander.option("-p, --print", "Evaluate script and print result");
 commander.option("-i, --ignore [regex]", "Ignore all files that match this regex when using the require hook");
 commander.option("-x, --extensions [extensions]", "List of extensions to hook into [.es6,.js]");
 commander.option("-r, --experimental", "Enable experimental support for proposed ES7 features");
+commander.option("-g, --playground", "Enable playground support");
 
 var pkg = require("../package.json");
 commander.version(pkg.version);
diff --git a/doc/playground.md b/doc/playground.md
new file mode 100644
index 0000000000..d98717a664
--- /dev/null
+++ b/doc/playground.md
@@ -0,0 +1,63 @@
+# Playground
+
+**Playground** is a  proving ground for possible ES7 proposals.
+
+**NOTE: These features are in no way endrosed by Ecma International and are not currently being proposed for any version of ECMAScript.** This may change in the future however.
+
+## Usage
+
+    $ 6to5 --playground
+
+```javascript
+to5.transform("code", { playground: true });
+```
+
+## Features
+
+ * [Memoization operator](#memoization-operator)
+ * [Method binding](#method-binding)
+
+### Memoization assignment operator
+
+```javascript
+var obj = {};
+obj.x ?= 2;
+obj.x; // 2
+
+obj = { x: 1 };
+obj.x ?= 2;
+obj.x; // 1
+
+obj = { x: undefined }
+obj.x ?= 2;
+obj.x; // undefined
+```
+
+```javascript
+var obj = {};
+obj.x ?= 2;
+```
+
+equivalent to:
+
+```javascript
+var obj = {};
+if (Object.prototype.hasOwnProperty.call(obj, "x")) obj.x = 2;
+```
+
+### Method binding expression.
+
+```javascript
+var fn = obj:method;
+var fn = obj:method("foob");
+```
+
+equivalent to:
+
+```javascript
+var fn = obj.method.bind(obj);
+var fn = obj.method.bind(obj, "foob");
+```
+
+**NOTE:** Method binding can **only** be used as an **expression** and not as
+statement.
diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index 73c24af8e8..32e8f62384 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -23,7 +23,9 @@ File.declarations = [
   "interop-require",
   "to-array",
   "arguments-to-array",
-  "object-spread"
+  "object-spread",
+  "has-own",
+  "slice"
 ];
 
 File.normaliseOptions = function (opts) {
@@ -31,6 +33,7 @@ File.normaliseOptions = function (opts) {
 
   _.defaults(opts, {
     experimental: false,
+    playground:   false,
     whitespace:   true,
     blacklist:    [],
     whitelist:    [],
@@ -135,7 +138,11 @@ File.prototype.addDeclaration = function (name) {
   }
 
   var uid = this.generateUidIdentifier(name);
-  this.scope.push(name, uid, ref);
+  this.scope.push({
+    key: name,
+    id: uid,
+    init: ref
+  });
   return uid;
 };
 
diff --git a/lib/6to5/generation/generator.js b/lib/6to5/generation/generator.js
index 73511ec6a6..bf7a57223c 100644
--- a/lib/6to5/generation/generator.js
+++ b/lib/6to5/generation/generator.js
@@ -53,6 +53,7 @@ CodeGenerator.generators = {
   comprehensions:   require("./generators/comprehensions"),
   expressions:      require("./generators/expressions"),
   statements:       require("./generators/statements"),
+  playground:       require("./generators/playground"),
   classes:          require("./generators/classes"),
   methods:          require("./generators/methods"),
   modules:          require("./generators/modules"),
diff --git a/lib/6to5/generation/generators/playground.js b/lib/6to5/generation/generators/playground.js
new file mode 100644
index 0000000000..3742aa9f86
--- /dev/null
+++ b/lib/6to5/generation/generators/playground.js
@@ -0,0 +1,7 @@
+var _ = require("lodash");
+
+_.each(["BindMemberExpression"], function (type) {
+  exports[type] = function () {
+    throw new ReferenceError("Trying to render non-standard playground node " + JSON.stringify(type));
+  };
+});
diff --git a/lib/6to5/patch.js b/lib/6to5/patch.js
index d0f428c9d2..a6049df532 100644
--- a/lib/6to5/patch.js
+++ b/lib/6to5/patch.js
@@ -30,6 +30,14 @@ def("VirtualPropertyExpression")
   .field("object", def("Expression"))
   .field("property", or(def("Identifier"), def("Expression")));
 
+// Playground
+def("BindMemberExpression")
+  .bases("Expression")
+  .build("object", "property", "arguments")
+  .field("object", def("Expression"))
+  .field("property", or(def("Identifier"), def("Expression")))
+  .field("arguments", [def("Expression")]);
+
 types.finalize();
 
 var estraverse = require("estraverse");
diff --git a/lib/6to5/templates/has-own.js b/lib/6to5/templates/has-own.js
new file mode 100644
index 0000000000..9a4caad24a
--- /dev/null
+++ b/lib/6to5/templates/has-own.js
@@ -0,0 +1 @@
+Object.prototype.hasOwnProperty;
diff --git a/lib/6to5/templates/slice.js b/lib/6to5/templates/slice.js
new file mode 100644
index 0000000000..f35f3b503b
--- /dev/null
+++ b/lib/6to5/templates/slice.js
@@ -0,0 +1 @@
+Array.prototype.slice;
diff --git a/lib/6to5/transformation/transform.js b/lib/6to5/transformation/transform.js
index 4629a8bb76..d2117bde7d 100644
--- a/lib/6to5/transformation/transform.js
+++ b/lib/6to5/transformation/transform.js
@@ -36,7 +36,6 @@ _.each({
   arrowFunctions:            require("./transformers/es6-arrow-functions"),
   classes:                   require("./transformers/es6-classes"),
 
-  _propertyLiterals:         require("./transformers/_property-literals"),
   computedPropertyNames:     require("./transformers/es6-computed-property-names"),
 
   objectSpread:              require("./transformers/es7-object-spread"),
@@ -57,12 +56,18 @@ _.each({
 
   generators:                require("./transformers/es6-generators"),
 
+  // plyground
+  methodBinding:             require("./transformers/playground-method-binding"),
+  memoizationOperator:       require("./transformers/playground-memoization-operator"),
+
   _blockHoist:               require("./transformers/_block-hoist"),
   _declarations:             require("./transformers/_declarations"),
   _aliasFunctions:           require("./transformers/_alias-functions"),
 
   useStrict:                 require("./transformers/use-strict"),
 
+  _propertyLiterals:         require("./transformers/_property-literals"),
+  _memberExpressioLiterals:  require("./transformers/_member-expression-literals"),
   _memberExpressionKeywords: require("./transformers/_member-expression-keywords"),
   _moduleFormatter:          require("./transformers/_module-formatter")
 }, function (transformer, key) {
diff --git a/lib/6to5/transformation/transformers/_declarations.js b/lib/6to5/transformation/transformers/_declarations.js
index 9b7626aadc..6ccda90a1c 100644
--- a/lib/6to5/transformation/transformers/_declarations.js
+++ b/lib/6to5/transformation/transformers/_declarations.js
@@ -3,9 +3,21 @@ var _ = require("lodash");
 
 exports.BlockStatement =
 exports.Program = function (node) {
+  var kinds = {};
+
   _.each(node._declarations, function (declar) {
-    node.body.unshift(t.variableDeclaration("var", [
-      t.variableDeclarator(declar.id, declar.init)
-    ]));
+    var kind = declar.kind || "var";
+    var declarNode = t.variableDeclarator(declar.id, declar.init);
+
+    if (!declar.init) {
+      kinds[kind] = kinds[kind] || [];
+      kinds[kind].push(declarNode);
+    } else {
+      node.body.unshift(t.variableDeclaration(kind, [declarNode]));
+    }
+  });
+
+  _.each(kinds, function (declars, kind) {
+    node.body.unshift(t.variableDeclaration(kind, declars));
   });
 };
diff --git a/lib/6to5/transformation/transformers/_member-expression-keywords.js b/lib/6to5/transformation/transformers/_member-expression-keywords.js
index feaaadaae0..46fb8b082f 100644
--- a/lib/6to5/transformation/transformers/_member-expression-keywords.js
+++ b/lib/6to5/transformation/transformers/_member-expression-keywords.js
@@ -1,5 +1,5 @@
 var esutils = require("esutils");
-var t = require("../../types");
+var t       = require("../../types");
 
 exports.MemberExpression = function (node) {
   var prop = node.property;
diff --git a/lib/6to5/transformation/transformers/_member-expression-literals.js b/lib/6to5/transformation/transformers/_member-expression-literals.js
new file mode 100644
index 0000000000..0c784e8615
--- /dev/null
+++ b/lib/6to5/transformation/transformers/_member-expression-literals.js
@@ -0,0 +1,10 @@
+var t = require("../../types");
+
+exports.MemberExpression = function (node, parent) {
+  var prop = node.property;
+  if (node.computed && t.isLiteral(prop) && t.isValidIdentifier(prop.value)) {
+    // computed literal that is a valid identifier
+    node.property = t.identifier(prop.value);
+    node.computed = false;
+  }
+};
diff --git a/lib/6to5/transformation/transformers/_property-literals.js b/lib/6to5/transformation/transformers/_property-literals.js
index 2a80e3134f..a7b8313b25 100644
--- a/lib/6to5/transformation/transformers/_property-literals.js
+++ b/lib/6to5/transformation/transformers/_property-literals.js
@@ -3,13 +3,14 @@ var t       = require("../../types");
 var _       = require("lodash");
 
 exports.Property = function (node) {
-  // ignore key literals that are valid identifiers
   var key = node.key;
-  if (t.isLiteral(key) && _.isString(key.value) && esutils.keyword.isIdentifierName(key.value)) {
-    key.type = "Identifier";
-    key.name = key.value;
-    delete key.value;
-
+  if (t.isLiteral(key) && t.isValidIdentifier(key.value)) {
+    // property key is a literal but a valid identifier
+    node.key = t.identifier(key.value);
     node.computed = false;
+  } else if (t.isIdentifier(key) && esutils.keyword.isKeywordES6(key.name, true)) {
+    // property key is a keyword
+    node.key = t.literal(key.name);
+    node.computed = true;
   }
 };
diff --git a/lib/6to5/transformation/transformers/es6-destructuring.js b/lib/6to5/transformation/transformers/es6-destructuring.js
index 3747bc95b2..29d81afc97 100644
--- a/lib/6to5/transformation/transformers/es6-destructuring.js
+++ b/lib/6to5/transformation/transformers/es6-destructuring.js
@@ -3,11 +3,14 @@
 var t = require("../../types");
 var _ = require("lodash");
 
-var buildVariableAssign = function (kind, id, init) {
-  if (kind === false) {
+var buildVariableAssign = function (opts, id, init) {
+  var op = opts.operator;
+  if (t.isMemberExpression(id)) op = "=";
+
+  if (op) {
     return t.expressionStatement(t.assignmentExpression("=", id, init));
   } else {
-    return t.variableDeclaration(kind, [
+    return t.variableDeclaration(opts.kind, [
       t.variableDeclarator(id, init)
     ]);
   }
@@ -18,10 +21,8 @@ var push = function (opts, nodes, elem, parentId) {
     pushObjectPattern(opts, nodes, elem, parentId);
   } else if (t.isArrayPattern(elem)) {
     pushArrayPattern(opts, nodes, elem, parentId);
-  } else if (t.isMemberExpression(elem)) {
-    nodes.push(buildVariableAssign(false, elem, parentId));
   } else {
-    nodes.push(buildVariableAssign(opts.kind, elem, parentId));
+    nodes.push(buildVariableAssign(opts, elem, parentId));
   }
 };
 
@@ -43,7 +44,7 @@ var pushObjectPattern = function (opts, nodes, pattern, parentId) {
         keys = t.arrayExpression(keys);
 
         var value = t.callExpression(opts.file.addDeclaration("object-spread"), [parentId, keys]);
-        nodes.push(buildVariableAssign(opts.kind, prop.argument, value));
+        nodes.push(buildVariableAssign(opts, prop.argument, value));
     } else {
       var pattern2   = prop.value;
       var patternId2 = t.memberExpression(parentId, prop.key, prop.computed);
@@ -51,7 +52,7 @@ var pushObjectPattern = function (opts, nodes, pattern, parentId) {
       if (t.isPattern(pattern2)) {
         push(opts, nodes, pattern2, patternId2);
       } else {
-        nodes.push(buildVariableAssign(opts.kind, pattern2, patternId2));
+        nodes.push(buildVariableAssign(opts, pattern2, patternId2));
       }
     }
   });
@@ -177,7 +178,7 @@ exports.ExpressionStatement = function (node, parent, file, scope) {
   ]));
 
   push({
-    kind: false,
+    operator: expr.operator,
     file: file,
     scope: scope
   }, nodes, expr.left, ref);
@@ -190,33 +191,24 @@ exports.AssignmentExpression = function (node, parent, file, scope) {
   if (!t.isPattern(node.left)) return;
 
   var tempName = file.generateUid("temp", scope);
-  var temp = t.identifier(tempName);
-  scope.push(tempName, temp);
-
-  var nodes = [];
-  nodes.push(t.assignmentExpression("=", temp, node.right));
-
-  push({
-    kind: false,
-    file: file,
-    scope: scope
-  }, nodes, node.left, temp);
-
-  nodes.push(temp);
-
-  nodes = nodes.map(function (node) {
-    if (t.isExpressionStatement(node)) {
-      return node.expression;
-    } else if (t.isVariableDeclaration(node)) {
-      var declar = node.declarations[0];
-      scope.push(declar.id.name, declar.id);
-      return t.assignmentExpression("=", declar.id, declar.init);
-    } else {
-      return node;
-    }
+  var ref = t.identifier(tempName);
+  scope.push({
+    key: tempName,
+    id: ref
   });
 
-  return t.sequenceExpression(nodes);
+  var nodes = [];
+  nodes.push(t.assignmentExpression("=", ref, node.right));
+
+  push({
+    operator: node.operator,
+    file: file,
+    scope: scope
+  }, nodes, node.left, ref);
+
+  nodes.push(ref);
+
+  return t.toSequenceExpression(nodes, scope);
 };
 
 exports.VariableDeclaration = function (node, parent, file, scope) {
@@ -236,17 +228,18 @@ exports.VariableDeclaration = function (node, parent, file, scope) {
   _.each(node.declarations, function (declar) {
     var patternId = declar.init;
     var pattern   = declar.id;
+    var opts = {
+      kind:    node.kind,
+      nodes:   nodes,
+      pattern: pattern,
+      id:      patternId,
+      file:    file,
+      scope:   scope
+    };
     if (t.isPattern(pattern) && patternId) {
-      pushPattern({
-        kind:    node.kind,
-        nodes:   nodes,
-        pattern: pattern,
-        id:      patternId,
-        file:    file,
-        scope:   scope
-      });
+      pushPattern(opts);
     } else {
-      nodes.push(buildVariableAssign(node.kind, declar.id, declar.init));
+      nodes.push(buildVariableAssign(opts, declar.id, declar.init));
     }
   });
 
@@ -268,4 +261,3 @@ exports.VariableDeclaration = function (node, parent, file, scope) {
 
   return nodes;
 };
-
diff --git a/lib/6to5/transformation/transformers/es7-abstract-references.js b/lib/6to5/transformation/transformers/es7-abstract-references.js
index 6128710ed8..66720d18ac 100644
--- a/lib/6to5/transformation/transformers/es7-abstract-references.js
+++ b/lib/6to5/transformation/transformers/es7-abstract-references.js
@@ -32,7 +32,10 @@ exports.AssignmentExpression = function (node, parent, file, scope) {
     if (t.isDynamic(value)) {
       var tempName = file.generateUid("temp");
       temp = value = t.identifier(tempName);
-      scope.push(tempName, temp);
+      scope.push({
+        key: tempName,
+        id: temp
+      });
     }
   }
 
@@ -74,7 +77,10 @@ exports.CallExpression = function (node, parent, file, scope) {
     // we need to save `callee.object` so we can call it again
     var tempName = file.generateUid("temp");
     temp = t.identifier(tempName);
-    scope.push(tempName, temp);
+    scope.push({
+      key: tempName,
+      id: temp
+    });
   }
 
   var call = util.template("abstract-expression-call", {
diff --git a/lib/6to5/transformation/transformers/playground-memoization-operator.js b/lib/6to5/transformation/transformers/playground-memoization-operator.js
new file mode 100644
index 0000000000..5d6ec25ade
--- /dev/null
+++ b/lib/6to5/transformation/transformers/playground-memoization-operator.js
@@ -0,0 +1,90 @@
+var t = require("../../types");
+
+var isMemo = function (node) {
+  var is = t.isAssignmentExpression(node) && node.operator === "?=";
+  if (is) t.assertMemberExpression(node.left);
+  return is;
+};
+
+var getPropRef = function (nodes, prop, file, scope) {
+  if (t.isIdentifier(prop)) {
+    return t.literal(prop.name);
+  } else {
+    var temp = file.generateUidIdentifier("propKey", scope);
+    nodes.push(t.variableDeclaration("var", [
+      t.variableDeclarator(temp, prop)
+    ]));
+    return temp;
+  }
+};
+
+var getObjRef = function (nodes, obj, file, scope) {
+  if (t.isDynamic(obj)) {
+    var temp = file.generateUidIdentifier("obj", scope);
+    nodes.push(t.variableDeclaration("var", [
+      t.variableDeclarator(temp, obj)
+    ]));
+    return temp;
+  } else {
+    return obj;
+  }
+};
+
+var buildHasOwn = function (obj, prop, file) {
+  return t.unaryExpression(
+    "!",
+    t.callExpression(
+      t.memberExpression(file.addDeclaration("has-own"), t.identifier("call")),
+      [obj, prop]
+    ),
+    true
+  );
+};
+
+var buildAbsoluteRef = function (left, obj, prop) {
+  var computed = left.computed || t.isLiteral(prop);
+  return t.memberExpression(obj, prop, computed);
+};
+
+var buildAssignment = function (expr, obj, prop) {
+  return t.assignmentExpression("=", buildAbsoluteRef(expr.left, obj, prop), expr.right);
+};
+
+exports.ExpressionStatement = function (node, parent, file, scope) {
+  var expr = node.expression;
+  if (!isMemo(expr)) return;
+
+  var nodes = [];
+
+  var left = expr.left;
+  var obj  = getObjRef(nodes, left.object, file, scope);
+  var prop = getPropRef(nodes, left.property, file, scope);
+
+  nodes.push(t.ifStatement(
+    buildHasOwn(obj, prop, file),
+    t.expressionStatement(buildAssignment(expr, obj, prop))
+  ));
+
+  return nodes;
+};
+
+exports.AssignmentExpression = function (node, parent, file, scope) {
+  if (t.isExpressionStatement(parent)) return;
+  if (!isMemo(node)) return;
+
+  var nodes = [];
+
+  var left = node.left;
+  var obj  = getObjRef(nodes, left.object, file, scope);
+  var prop = getPropRef(nodes, left.property, file, scope);
+
+  nodes.push(t.logicalExpression(
+    "&&",
+    buildHasOwn(obj, prop, file),
+    buildAssignment(node, obj, prop)
+  ));
+
+  nodes.push(buildAbsoluteRef(left, obj, prop));
+
+  return t.toSequenceExpression(nodes, scope);
+};
diff --git a/lib/6to5/transformation/transformers/playground-method-binding.js b/lib/6to5/transformation/transformers/playground-method-binding.js
new file mode 100644
index 0000000000..2faad64af9
--- /dev/null
+++ b/lib/6to5/transformation/transformers/playground-method-binding.js
@@ -0,0 +1,30 @@
+var t = require("../../types");
+
+exports.BindMemberExpression = function (node, parent, file, scope) {
+  var object = node.object;
+  var prop   = node.property;
+
+  var temp;
+  if (t.isDynamic(object)) {
+    var tempName = file.generateUid("temp", scope);
+    temp =  object = t.identifier(tempName);
+    scope.push({
+      key: tempName,
+      id: temp
+    });
+  }
+
+  var call = t.callExpression(
+    t.memberExpression(t.memberExpression(object, prop), t.identifier("bind")),
+    [object].concat(node.arguments)
+  );
+
+  if (temp) {
+    return t.sequenceExpression([
+      t.assignmentExpression("=", temp, node.object),
+      call
+    ]);
+  } else {
+    return call;
+  }
+};
diff --git a/lib/6to5/traverse/scope.js b/lib/6to5/traverse/scope.js
index d20b5aba56..9666edafa3 100644
--- a/lib/6to5/traverse/scope.js
+++ b/lib/6to5/traverse/scope.js
@@ -101,7 +101,7 @@ Scope.prototype.getReferences = function () {
   return references;
 };
 
-Scope.prototype.push = function (name, id, init) {
+Scope.prototype.push = function (opts) {
   var block = this.block;
 
   if (t.isFor(block) || t.isCatchClause(block) || t.isFunction(block)) {
@@ -111,9 +111,10 @@ Scope.prototype.push = function (name, id, init) {
 
   if (t.isBlockStatement(block) || t.isProgram(block)) {
     block._declarations = block._declarations || {};
-    block._declarations[name] = {
-      id: id,
-      init: init
+    block._declarations[opts.key] = {
+      kind: opts.kind,
+      id: opts.id,
+      init: opts.init
     };
   } else {
     throw new TypeError("cannot add a declaration here in node type " + block.type);
diff --git a/lib/6to5/types/builder-keys.json b/lib/6to5/types/builder-keys.json
index 91527d5b2a..45c315a50b 100644
--- a/lib/6to5/types/builder-keys.json
+++ b/lib/6to5/types/builder-keys.json
@@ -11,6 +11,7 @@
   "Identifier":              ["name"],
   "IfStatement":             ["test", "consequent", "alternate"],
   "Literal":                 ["value"],
+  "LogicalExpression":       ["operator", "left", "right"],
   "MemberExpression":        ["object", "property", "computed"],
   "NewExpression":           ["callee", "arguments"],
   "ObjectExpression":        ["properties"],
diff --git a/lib/6to5/types/index.js b/lib/6to5/types/index.js
index 82f4af15d3..3ed12a6e47 100644
--- a/lib/6to5/types/index.js
+++ b/lib/6to5/types/index.js
@@ -1,4 +1,5 @@
-var _ = require("lodash");
+var esutils = require("esutils");
+var _       = require("lodash");
 
 var t = exports;
 
@@ -71,6 +72,31 @@ addAssert("Expression", t.isExpression);
 
 //
 
+t.toSequenceExpression = function (nodes, scope) {
+  var exprs = [];
+
+  _.each(nodes, function (node) {
+    if (t.isExpression(node)) {
+      exprs.push(node);
+    } if (t.isExpressionStatement(node)) {
+      exprs.push(node.expression);
+    } else if (t.isVariableDeclaration(node)) {
+      _.each(node.declarations, function (declar) {
+        scope.push({
+          kind: node.kind,
+          key: declar.id.name,
+          id: declar.id
+        });
+        exprs.push(t.assignmentExpression("=", declar.id, declar.init));
+      });
+    }
+  });
+
+  return t.sequenceExpression(exprs);
+};
+
+//
+
 t.shallowEqual = function (actual, expected) {
   var same = true;
 
@@ -135,6 +161,10 @@ t.toIdentifier = function (name) {
   return name;
 };
 
+t.isValidIdentifier = function (name) {
+  return _.isString(name) && esutils.keyword.isIdentifierName(name) && !esutils.keyword.isKeywordES6(name, true);
+};
+
 t.ensureBlock = function (node) {
   node.body = t.toBlock(node.body, node);
 };
diff --git a/lib/6to5/types/visitor-keys.json b/lib/6to5/types/visitor-keys.json
index 02808567f5..79a3902c5f 100644
--- a/lib/6to5/types/visitor-keys.json
+++ b/lib/6to5/types/visitor-keys.json
@@ -5,6 +5,7 @@
   "AssignmentExpression":      ["left", "right"],
   "AwaitExpression":           ["argument"],
   "BinaryExpression":          ["left", "right"],
+  "BindMemberExpression":      ["object", "property", "arguments"],
   "BlockStatement":            ["body"],
   "BreakStatement":            ["label"],
   "CallExpression":            ["callee", "arguments"],
diff --git a/lib/6to5/util.js b/lib/6to5/util.js
index e698078268..244ab28cab 100644
--- a/lib/6to5/util.js
+++ b/lib/6to5/util.js
@@ -219,6 +219,7 @@ exports.parse = function (opts, code, callback) {
       allowReturnOutsideFunction: true,
       preserveParens:             true,
       ecmaVersion:                opts.experimental ? 7 : 6,
+      playground:                 opts.playground,
       strictMode:                 true,
       onComment:                  comments,
       locations:                  true,
diff --git a/package.json b/package.json
index 76b9745829..3b140220b3 100644
--- a/package.json
+++ b/package.json
@@ -47,7 +47,7 @@
     "chokidar": "0.11.1",
     "source-map-support": "0.2.8",
     "esutils": "1.1.6",
-    "acorn-6to5": "0.9.1-7",
+    "acorn-6to5": "0.9.1-8",
     "estraverse": "1.8.0",
     "private": "0.1.6"
   },
diff --git a/test/fixtures/transformation/api/blacklist/actual.js b/test/fixtures/transformation/api/blacklist/actual.js
index deaf9a91ef..8ec84a062e 100644
--- a/test/fixtures/transformation/api/blacklist/actual.js
+++ b/test/fixtures/transformation/api/blacklist/actual.js
@@ -1,5 +1,5 @@
 class Test {
   constructor() {
-  arr.map(x => x * x);
+    arr.map(x => x * x);
   }
 }
diff --git a/test/fixtures/transformation/api/blacklist/untitled b/test/fixtures/transformation/api/blacklist/untitled
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js b/test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js
index 882a44fb84..ff82bc596a 100644
--- a/test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js
+++ b/test/fixtures/transformation/es6-destructuring/assignment-expression/expected.js
@@ -1,9 +1,8 @@
 "use strict";
 
-var _ref;
+var _temp, _ref;
 var _toArray = function (arr) {
   return Array.isArray(arr) ? arr : Array.from(arr);
 };
 
-var _temp;
 console.log((_temp = [123], _ref = _toArray(_temp), x = _ref[0], _temp));
diff --git a/test/fixtures/transformation/misc/_member-expression-keywords/expected.js b/test/fixtures/transformation/misc/_member-expression-keywords/expected.js
index e603ba03f8..fdd217784a 100644
--- a/test/fixtures/transformation/misc/_member-expression-keywords/expected.js
+++ b/test/fixtures/transformation/misc/_member-expression-keywords/expected.js
@@ -1,6 +1,6 @@
 "use strict";
 
 test["catch"];
-test["catch"]["foo"];
+test["catch"].foo;
 test["catch"];
-test["catch"]["foo"];
+test["catch"].foo;
diff --git a/test/fixtures/transformation/misc/_member-expression-literals/actual.js b/test/fixtures/transformation/misc/_member-expression-literals/actual.js
new file mode 100644
index 0000000000..c855363128
--- /dev/null
+++ b/test/fixtures/transformation/misc/_member-expression-literals/actual.js
@@ -0,0 +1 @@
+obj["x"] = 2;
diff --git a/test/fixtures/transformation/misc/_member-expression-literals/expected.js b/test/fixtures/transformation/misc/_member-expression-literals/expected.js
new file mode 100644
index 0000000000..0a18f3d810
--- /dev/null
+++ b/test/fixtures/transformation/misc/_member-expression-literals/expected.js
@@ -0,0 +1,3 @@
+"use strict";
+
+obj.x = 2;
diff --git a/test/fixtures/transformation/playground/memoization-assignment-operator/actual.js b/test/fixtures/transformation/playground/memoization-assignment-operator/actual.js
new file mode 100644
index 0000000000..b2d1521e2c
--- /dev/null
+++ b/test/fixtures/transformation/playground/memoization-assignment-operator/actual.js
@@ -0,0 +1,13 @@
+var obj = {};
+
+obj.x ?= 2;
+
+console.log(obj.x ?= 2);
+
+obj[x()] ?= 2;
+
+console.log(obj[x()] ?= 2);
+
+obj[y()][x()] ?= 2;
+
+console.log(obj[y()][x()] ?= 2);
diff --git a/test/fixtures/transformation/playground/memoization-assignment-operator/exec.js b/test/fixtures/transformation/playground/memoization-assignment-operator/exec.js
new file mode 100644
index 0000000000..3e528c641d
--- /dev/null
+++ b/test/fixtures/transformation/playground/memoization-assignment-operator/exec.js
@@ -0,0 +1,20 @@
+var obj = {};
+obj.x ?= 2;
+assert.equal(obj.x, 2);
+
+obj = {};
+assert.equal(obj.x ?= 2, 2);
+
+obj = { x: 1 };
+obj.x ?= 2;
+assert.equal(obj.x, 1);
+
+obj = { x: 1 };
+assert.equal(obj.x ?= 2, 1);
+
+obj = { x: undefined }
+obj.x ?= 2;
+assert.equal(obj.x, undefined);
+
+obj = { x: undefined }
+assert.equal(obj.x ?= 2, undefined);
diff --git a/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js b/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
new file mode 100644
index 0000000000..e00aea8c5e
--- /dev/null
+++ b/test/fixtures/transformation/playground/memoization-assignment-operator/expected.js
@@ -0,0 +1,25 @@
+"use strict";
+
+var _propKey2, _obj2, _propKey4;
+var _hasOwn = Object.prototype.hasOwnProperty;
+var obj = {};
+
+if (!_hasOwn.call(obj, "x")) obj.x = 2;
+
+
+console.log((!_hasOwn.call(obj, "x") && (obj.x = 2), obj.x));
+
+var _propKey = x();
+
+if (!_hasOwn.call(obj, _propKey)) obj[_propKey] = 2;
+
+
+console.log((_propKey2 = x(), !_hasOwn.call(obj, _propKey2) && (obj[_propKey2] = 2), obj[_propKey2]));
+
+var _obj = obj[y()];
+var _propKey3 = x();
+
+if (!_hasOwn.call(_obj, _propKey3)) _obj[_propKey3] = 2;
+
+
+console.log((_obj2 = obj[y()], _propKey4 = x(), !_hasOwn.call(_obj2, _propKey4) && (_obj2[_propKey4] = 2), _obj2[_propKey4]));
diff --git a/test/fixtures/transformation/playground/method-binding/actual.js b/test/fixtures/transformation/playground/method-binding/actual.js
new file mode 100644
index 0000000000..c3f896ba9a
--- /dev/null
+++ b/test/fixtures/transformation/playground/method-binding/actual.js
@@ -0,0 +1,5 @@
+var fn = obj:method;
+var fn = obj:method("foob");
+var fn = obj[foo]:method;
+var fn = obj.foo:method;
+var fn = obj[foo()]:method;
diff --git a/test/fixtures/transformation/playground/method-binding/exec.js b/test/fixtures/transformation/playground/method-binding/exec.js
new file mode 100644
index 0000000000..3446ce1a25
--- /dev/null
+++ b/test/fixtures/transformation/playground/method-binding/exec.js
@@ -0,0 +1,22 @@
+var obj = {
+  foo: "foo",
+  bar: "bar",
+  getFoo: function () {
+    return this.foo;
+  },
+  getBar: function (arg) {
+    return arg + " " +  this.bar;
+  },
+  getZoo: function (a, b) {
+    return this.foo + " " + this.bar + " " + a + " " + b;
+  }
+};
+
+var foo = obj:getFoo;
+assert.equal(foo(), "foo");
+
+var bar = obj:getBar("foo");
+assert.equal(bar(), "foo bar");
+
+var zoo = obj:getZoo("foo");
+assert.equal(zoo("bar"), "foo bar foo bar");
diff --git a/test/fixtures/transformation/playground/method-binding/expected.js b/test/fixtures/transformation/playground/method-binding/expected.js
new file mode 100644
index 0000000000..eed4dfd16e
--- /dev/null
+++ b/test/fixtures/transformation/playground/method-binding/expected.js
@@ -0,0 +1,8 @@
+"use strict";
+
+var _temp;
+var fn = obj.method.bind(obj);
+var fn = obj.method.bind(obj, "foob");
+var fn = obj[foo].method.bind(obj[foo]);
+var fn = obj.foo.method.bind(obj.foo);
+var fn = (_temp = obj[foo()], _temp.method.bind(_temp));
diff --git a/test/fixtures/transformation/playground/options.json b/test/fixtures/transformation/playground/options.json
new file mode 100644
index 0000000000..e68df25688
--- /dev/null
+++ b/test/fixtures/transformation/playground/options.json
@@ -0,0 +1,3 @@
+{
+  "playground": true
+}
diff --git a/test/transformation.js b/test/transformation.js
index dc9d54c125..388097e447 100644
--- a/test/transformation.js
+++ b/test/transformation.js
@@ -37,10 +37,11 @@ var run = function (task, done) {
       err.message += util.codeFrame(execCode);
       throw err;
     }
-  } else {
-    var actualCode = actual.code;
-    var expectCode = expect.code;
+  }
 
+  var actualCode = actual.code;
+  var expectCode = expect.code;
+  if (!execCode || actualCode) {
     result     = transform(actualCode, getOpts(actual));
     actualCode = result.code;