diff --git a/src/blocks/scratch3_control.js b/src/blocks/scratch3_control.js
index cbfe61a24..28737b361 100644
--- a/src/blocks/scratch3_control.js
+++ b/src/blocks/scratch3_control.js
@@ -11,7 +11,7 @@ var Scratch3ControlBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3ControlBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_data.js b/src/blocks/scratch3_data.js
index 55a6b8bb7..b17835638 100644
--- a/src/blocks/scratch3_data.js
+++ b/src/blocks/scratch3_data.js
@@ -10,7 +10,7 @@ var Scratch3DataBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3DataBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_event.js b/src/blocks/scratch3_event.js
index 8bfef42c2..b4c40116e 100644
--- a/src/blocks/scratch3_event.js
+++ b/src/blocks/scratch3_event.js
@@ -10,7 +10,7 @@ var Scratch3EventBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3EventBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_looks.js b/src/blocks/scratch3_looks.js
index 60d95fd50..c7a9fcadf 100644
--- a/src/blocks/scratch3_looks.js
+++ b/src/blocks/scratch3_looks.js
@@ -10,7 +10,7 @@ var Scratch3LooksBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3LooksBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_motion.js b/src/blocks/scratch3_motion.js
index be96e9cd8..857644dd5 100644
--- a/src/blocks/scratch3_motion.js
+++ b/src/blocks/scratch3_motion.js
@@ -12,7 +12,7 @@ var Scratch3MotionBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3MotionBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_operators.js b/src/blocks/scratch3_operators.js
index d51e30894..fce7fb3a7 100644
--- a/src/blocks/scratch3_operators.js
+++ b/src/blocks/scratch3_operators.js
@@ -11,7 +11,7 @@ var Scratch3OperatorsBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3OperatorsBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_pen.js b/src/blocks/scratch3_pen.js
index 6ef00cf71..c8f98341e 100644
--- a/src/blocks/scratch3_pen.js
+++ b/src/blocks/scratch3_pen.js
@@ -163,7 +163,7 @@ Scratch3PenBlocks.prototype._wrapHueOrShade = function (value) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3PenBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_procedures.js b/src/blocks/scratch3_procedures.js
index 62c7b8dbe..471205f48 100644
--- a/src/blocks/scratch3_procedures.js
+++ b/src/blocks/scratch3_procedures.js
@@ -8,7 +8,7 @@ var Scratch3ProcedureBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3ProcedureBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_sensing.js b/src/blocks/scratch3_sensing.js
index c940c5068..1601fc650 100644
--- a/src/blocks/scratch3_sensing.js
+++ b/src/blocks/scratch3_sensing.js
@@ -10,7 +10,7 @@ var Scratch3SensingBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3SensingBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/blocks/scratch3_sound.js b/src/blocks/scratch3_sound.js
index f1a16f179..7e1e466a0 100644
--- a/src/blocks/scratch3_sound.js
+++ b/src/blocks/scratch3_sound.js
@@ -11,7 +11,7 @@ var Scratch3SoundBlocks = function (runtime) {
 
 /**
  * Retrieve the block primitives implemented by this package.
- * @return {Object.<string, Function>} Mapping of opcode to Function.
+ * @return {object.<string, Function>} Mapping of opcode to Function.
  */
 Scratch3SoundBlocks.prototype.getPrimitives = function () {
     return {
diff --git a/src/engine/adapter.js b/src/engine/adapter.js
index e68cd3ea5..56275e1cb 100644
--- a/src/engine/adapter.js
+++ b/src/engine/adapter.js
@@ -6,7 +6,7 @@ var html = require('htmlparser2');
  * to a usable form for the Scratch runtime.
  * This structure is based on Blockly xml.js:`domToWorkspace` and `domToBlock`.
  * @param {Element} blocksDOM DOM tree for this event.
- * @return {Array.<Object>} Usable list of blocks from this CREATE event.
+ * @return {Array.<object>} Usable list of blocks from this CREATE event.
  */
 var domToBlocks = function (blocksDOM) {
     // At this level, there could be multiple blocks adjacent in the DOM tree.
@@ -32,8 +32,8 @@ var domToBlocks = function (blocksDOM) {
 /**
  * Adapter between block creation events and block representation which can be
  * used by the Scratch runtime.
- * @param {Object} e `Blockly.events.create`
- * @return {Array.<Object>} List of blocks from this CREATE event.
+ * @param {object} e `Blockly.events.create`
+ * @return {Array.<object>} List of blocks from this CREATE event.
  */
 var adapter = function (e) {
     // Validate input
@@ -47,8 +47,8 @@ var adapter = function (e) {
  * Convert and an individual block DOM to the representation tree.
  * Based on Blockly's `domToBlockHeadless_`.
  * @param {Element} blockDOM DOM tree for an individual block.
- * @param {Object} blocks Collection of blocks to add to.
- * @param {Boolean} isTopBlock Whether blocks at this level are "top blocks."
+ * @param {object} blocks Collection of blocks to add to.
+ * @param {boolean} isTopBlock Whether blocks at this level are "top blocks."
  * @param {?string} parent Parent block ID.
  * @return {undefined}
  */
diff --git a/src/engine/blocks.js b/src/engine/blocks.js
index d2215a2cc..ed03be324 100644
--- a/src/engine/blocks.js
+++ b/src/engine/blocks.js
@@ -34,7 +34,7 @@ Blocks.BRANCH_INPUT_PREFIX = 'SUBSTACK';
 /**
  * Provide an object with metadata for the requested block ID.
  * @param {!string} blockId ID of block we have stored.
- * @return {?Object} Metadata about the block, if it exists.
+ * @return {?object} Metadata about the block, if it exists.
  */
 Blocks.prototype.getBlock = function (blockId) {
     return this._blocks[blockId];
@@ -92,7 +92,7 @@ Blocks.prototype.getOpcode = function (id) {
 /**
  * Get all fields and their values for a block.
  * @param {?string} id ID of block to query.
- * @return {!Object} All fields and their values.
+ * @return {!object} All fields and their values.
  */
 Blocks.prototype.getFields = function (id) {
     var block = this._blocks[id];
@@ -102,7 +102,7 @@ Blocks.prototype.getFields = function (id) {
 /**
  * Get all non-branch inputs for a block.
  * @param {?string} id ID of block to query.
- * @return {!Object} All non-branch inputs and their associated blocks.
+ * @return {!object} All non-branch inputs and their associated blocks.
  */
 Blocks.prototype.getInputs = function (id) {
     var block = this._blocks[id];
@@ -121,7 +121,7 @@ Blocks.prototype.getInputs = function (id) {
 /**
  * Get mutation data for a block.
  * @param {?string} id ID of block to query.
- * @return {!Object} Mutation for the block.
+ * @return {!object} Mutation for the block.
  */
 Blocks.prototype.getMutation = function (id) {
     var block = this._blocks[id];
@@ -247,7 +247,7 @@ Blocks.prototype.blocklyListen = function (e, optRuntime) {
 
 /**
  * Block management: create blocks and scripts from a `create` event
- * @param {!Object} block Blockly create event to be processed
+ * @param {!object} block Blockly create event to be processed
  */
 Blocks.prototype.createBlock = function (block) {
     // Does the block already exist?
@@ -267,7 +267,7 @@ Blocks.prototype.createBlock = function (block) {
 
 /**
  * Block management: change block field values
- * @param {!Object} args Blockly change event to be processed
+ * @param {!object} args Blockly change event to be processed
  */
 Blocks.prototype.changeBlock = function (args) {
     // Validate
@@ -286,7 +286,7 @@ Blocks.prototype.changeBlock = function (args) {
 
 /**
  * Block management: move blocks from parent to parent
- * @param {!Object} e Blockly move event to be processed
+ * @param {!object} e Blockly move event to be processed
  */
 Blocks.prototype.moveBlock = function (e) {
     if (!this._blocks.hasOwnProperty(e.id)) {
@@ -342,7 +342,7 @@ Blocks.prototype.moveBlock = function (e) {
 
 /**
  * Block management: delete blocks and their associated scripts.
- * @param {!Object} e Blockly delete event to be processed.
+ * @param {!object} e Blockly delete event to be processed.
  */
 Blocks.prototype.deleteBlock = function (e) {
     // @todo In runtime, stop threads running on this script.
@@ -449,7 +449,7 @@ Blocks.prototype.blockToXML = function (blockId) {
 
 /**
  * Recursively encode a mutation object to XML.
- * @param {!Object} mutation Object representing a mutation.
+ * @param {!object} mutation Object representing a mutation.
  * @return {string} XML string representing a mutation.
  */
 Blocks.prototype.mutationToXML = function (mutation) {
diff --git a/src/engine/execute.js b/src/engine/execute.js
index a8967eb1f..44951aba3 100644
--- a/src/engine/execute.js
+++ b/src/engine/execute.js
@@ -4,7 +4,7 @@ var Thread = require('./thread');
 /**
  * Utility function to determine if a value is a Promise.
  * @param {*} value Value to check for a Promise.
- * @return {Boolean} True if the value appears to be a Promise.
+ * @return {boolean} True if the value appears to be a Promise.
  */
 var isPromise = function (value) {
     return value && value.then && typeof value.then === 'function';
diff --git a/src/engine/mutation-adapter.js b/src/engine/mutation-adapter.js
index 9277cc150..54bf7b4ee 100644
--- a/src/engine/mutation-adapter.js
+++ b/src/engine/mutation-adapter.js
@@ -2,8 +2,8 @@ var html = require('htmlparser2');
 
 /**
  * Convert a part of a mutation DOM to a mutation VM object, recursively.
- * @param {Object} dom DOM object for mutation tag.
- * @return {Object} Object representing useful parts of this mutation.
+ * @param {object} dom DOM object for mutation tag.
+ * @return {object} Object representing useful parts of this mutation.
  */
 var mutatorTagToObject = function (dom) {
     var obj = Object.create(null);
@@ -24,8 +24,8 @@ var mutatorTagToObject = function (dom) {
 /**
  * Adapter between mutator XML or DOM and block representation which can be
  * used by the Scratch runtime.
- * @param {(Object|string)} mutation Mutation XML string or DOM.
- * @return {Object} Object representing the mutation.
+ * @param {(object|string)} mutation Mutation XML string or DOM.
+ * @return {object} Object representing the mutation.
  */
 var mutationAdpater = function (mutation) {
     var mutationParsed;
diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index 3a1967baa..f196a6a69 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -276,7 +276,7 @@ Runtime.prototype.getOpcodeFunction = function (opcode) {
 /**
  * Return whether an opcode represents a hat block.
  * @param {!string} opcode The opcode to look up.
- * @return {Boolean} True if the op is known to be a hat.
+ * @return {boolean} True if the op is known to be a hat.
  */
 Runtime.prototype.getIsHat = function (opcode) {
     return this._hats.hasOwnProperty(opcode);
@@ -285,7 +285,7 @@ Runtime.prototype.getIsHat = function (opcode) {
 /**
  * Return whether an opcode represents an edge-activated hat block.
  * @param {!string} opcode The opcode to look up.
- * @return {Boolean} True if the op is known to be a edge-activated hat.
+ * @return {boolean} True if the op is known to be a edge-activated hat.
  */
 Runtime.prototype.getIsEdgeActivatedHat = function (opcode) {
     return this._hats.hasOwnProperty(opcode) &&
@@ -379,7 +379,7 @@ Runtime.prototype._restartThread = function (thread) {
 /**
  * Return whether a thread is currently active/running.
  * @param {?Thread} thread Thread object to check.
- * @return {Boolean} True if the thread is active/running.
+ * @return {boolean} True if the thread is active/running.
  */
 Runtime.prototype.isActiveThread = function (thread) {
     return this.threads.indexOf(thread) > -1;
@@ -427,7 +427,7 @@ Runtime.prototype.allScriptsDo = function (f, optTarget) {
 /**
  * Start all relevant hats.
  * @param {!string} requestedHatOpcode Opcode of hats to start.
- * @param {Object=} optMatchFields Optionally, fields to match on the hat.
+ * @param {object=} optMatchFields Optionally, fields to match on the hat.
  * @param {Target=} optTarget Optionally, a target to restrict to.
  * @return {Array.<Thread>} List of threads started by this function.
  */
diff --git a/src/engine/sequencer.js b/src/engine/sequencer.js
index 79476ba6f..06deb38f9 100644
--- a/src/engine/sequencer.js
+++ b/src/engine/sequencer.js
@@ -171,8 +171,8 @@ Sequencer.prototype.stepThread = function (thread) {
 /**
  * Step a thread into a block's branch.
  * @param {!Thread} thread Thread object to step to branch.
- * @param {Number} branchNum Which branch to step to (i.e., 1, 2).
- * @param {Boolean} isLoop Whether this block is a loop.
+ * @param {number} branchNum Which branch to step to (i.e., 1, 2).
+ * @param {boolean} isLoop Whether this block is a loop.
  */
 Sequencer.prototype.stepToBranch = function (thread, branchNum, isLoop) {
     if (!branchNum) {
diff --git a/src/engine/thread.js b/src/engine/thread.js
index 8bef97496..9693b26f1 100644
--- a/src/engine/thread.js
+++ b/src/engine/thread.js
@@ -151,7 +151,7 @@ Thread.prototype.peekStack = function () {
 
 /**
  * Get top stack frame.
- * @return {?Object} Last stack frame stored on this thread.
+ * @return {?object} Last stack frame stored on this thread.
  */
 Thread.prototype.peekStackFrame = function () {
     return this.stackFrames.length > 0 ? this.stackFrames[this.stackFrames.length - 1] : null;
@@ -159,7 +159,7 @@ Thread.prototype.peekStackFrame = function () {
 
 /**
  * Get stack frame above the current top.
- * @return {?Object} Second to last stack frame stored on this thread.
+ * @return {?object} Second to last stack frame stored on this thread.
  */
 Thread.prototype.peekParentStackFrame = function () {
     return this.stackFrames.length > 1 ? this.stackFrames[this.stackFrames.length - 2] : null;
@@ -205,7 +205,7 @@ Thread.prototype.getParam = function (paramName) {
 
 /**
  * Whether the current execution of a thread is at the top of the stack.
- * @return {Boolean} True if execution is at top of the stack.
+ * @return {boolean} True if execution is at top of the stack.
  */
 Thread.prototype.atStackTop = function () {
     return this.peekStack() === this.topBlock;
diff --git a/src/engine/variable.js b/src/engine/variable.js
index 65fc21c45..3f2dcc5de 100644
--- a/src/engine/variable.js
+++ b/src/engine/variable.js
@@ -5,7 +5,7 @@
 
 /**
  * @param {!string} name Name of the variable.
- * @param {(string|Number)} value Value of the variable.
+ * @param {(string|number)} value Value of the variable.
  * @param {boolean} isCloud Whether the variable is stored in the cloud.
  * @constructor
  */
diff --git a/src/import/sb2import.js b/src/import/sb2import.js
index 13983d569..40c17e309 100644
--- a/src/import/sb2import.js
+++ b/src/import/sb2import.js
@@ -17,7 +17,7 @@ var List = require('../engine/list');
 
 /**
  * Parse a single "Scratch object" and create all its in-memory VM objects.
- * @param {!Object} object From-JSON "Scratch object:" sprite, stage, watcher.
+ * @param {!object} object From-JSON "Scratch object:" sprite, stage, watcher.
  * @param {!Runtime} runtime Runtime object to load all structures into.
  * @param {boolean} topLevel Whether this is the top-level object (stage).
  * @return {?Target} Target created (stage or sprite).
@@ -138,7 +138,7 @@ var parseScratchObject = function (object, runtime, topLevel) {
  * and process the top-level object (the stage object).
  * @param {!string} json SB2-format JSON to load.
  * @param {!Runtime} runtime Runtime object to load all structures into.
- * @param {Boolean=} optForceSprite If set, treat as sprite (Sprite2).
+ * @param {boolean=} optForceSprite If set, treat as sprite (Sprite2).
  * @return {?Target} Top-level target created (stage or sprite).
  */
 var sb2import = function (json, runtime, optForceSprite) {
@@ -152,7 +152,7 @@ var sb2import = function (json, runtime, optForceSprite) {
 /**
  * Parse a Scratch object's scripts into VM blocks.
  * This should only handle top-level scripts that include X, Y coordinates.
- * @param {!Object} scripts Scripts object from SB2 JSON.
+ * @param {!object} scripts Scripts object from SB2 JSON.
  * @param {!Blocks} blocks Blocks object to load parsed blocks into.
  */
 var parseScripts = function (scripts, blocks) {
@@ -184,8 +184,8 @@ var parseScripts = function (scripts, blocks) {
  * Could be used to parse a top-level script,
  * a list of blocks in a branch (e.g., in forever),
  * or a list of blocks in an argument (e.g., move [pick random...]).
- * @param {Array.<Object>} blockList SB2 JSON-format block list.
- * @return {Array.<Object>} Scratch VM-format block list.
+ * @param {Array.<object>} blockList SB2 JSON-format block list.
+ * @return {Array.<object>} Scratch VM-format block list.
  */
 var parseBlockList = function (blockList) {
     var resultingList = [];
@@ -207,8 +207,8 @@ var parseBlockList = function (blockList) {
 /**
  * Flatten a block tree into a block list.
  * Children are temporarily stored on the `block.children` property.
- * @param {Array.<Object>} blocks list generated by `parseBlockList`.
- * @return {Array.<Object>} Flattened list to be passed to `blocks.createBlock`.
+ * @param {Array.<object>} blocks list generated by `parseBlockList`.
+ * @return {Array.<object>} Flattened list to be passed to `blocks.createBlock`.
  */
 var flatten = function (blocks) {
     var finalBlocks = [];
@@ -228,7 +228,7 @@ var flatten = function (blocks) {
  * into an argument map. This allows us to provide the expected inputs
  * to a mutated procedure call.
  * @param {string} procCode Scratch 2.0 procedure string.
- * @return {Object} Argument map compatible with those in sb2specmap.
+ * @return {object} Argument map compatible with those in sb2specmap.
  */
 var parseProcedureArgMap = function (procCode) {
     var argMap = [
@@ -259,8 +259,8 @@ var parseProcedureArgMap = function (procCode) {
 
 /**
  * Parse a single SB2 JSON-formatted block and its children.
- * @param {!Object} sb2block SB2 JSON-formatted block.
- * @return {Object} Scratch VM format block.
+ * @param {!object} sb2block SB2 JSON-formatted block.
+ * @return {object} Scratch VM format block.
  */
 var parseBlock = function (sb2block) {
     // First item in block object is the old opcode (e.g., 'forward:').
diff --git a/src/sprites/rendered-target.js b/src/sprites/rendered-target.js
index 9eb8956b2..b82afa846 100644
--- a/src/sprites/rendered-target.js
+++ b/src/sprites/rendered-target.js
@@ -184,7 +184,7 @@ RenderedTarget.prototype.setXY = function (x, y) {
 
 /**
  * Get the rendered direction and scale, after applying rotation style.
- * @return {Object<string, number>} Direction and scale to render.
+ * @return {object<string, number>} Direction and scale to render.
  */
 RenderedTarget.prototype._getRenderedDirectionAndScale = function () {
     // Default: no changes to `this.direction` or `this.scale`.
@@ -480,7 +480,7 @@ RenderedTarget.prototype.isSprite = function () {
 /**
  * Return the rendered target's tight bounding box.
  * Includes top, left, bottom, right attributes in Scratch coordinates.
- * @return {?Object} Tight bounding box, or null.
+ * @return {?object} Tight bounding box, or null.
  */
 RenderedTarget.prototype.getBounds = function () {
     if (this.renderer) {
@@ -493,7 +493,7 @@ RenderedTarget.prototype.getBounds = function () {
  * Return whether touching a point.
  * @param {number} x X coordinate of test point.
  * @param {number} y Y coordinate of test point.
- * @return {Boolean} True iff the rendered target is touching the point.
+ * @return {boolean} True iff the rendered target is touching the point.
  */
 RenderedTarget.prototype.isTouchingPoint = function (x, y) {
     if (this.renderer) {
@@ -513,7 +513,7 @@ RenderedTarget.prototype.isTouchingPoint = function (x, y) {
 
 /**
  * Return whether touching a stage edge.
- * @return {Boolean} True iff the rendered target is touching the stage edge.
+ * @return {boolean} True iff the rendered target is touching the stage edge.
  */
 RenderedTarget.prototype.isTouchingEdge = function () {
     if (this.renderer) {
@@ -533,7 +533,7 @@ RenderedTarget.prototype.isTouchingEdge = function () {
 /**
  * Return whether touching any of a named sprite's clones.
  * @param {string} spriteName Name of the sprite.
- * @return {Boolean} True iff touching a clone of the sprite.
+ * @return {boolean} True iff touching a clone of the sprite.
  */
 RenderedTarget.prototype.isTouchingSprite = function (spriteName) {
     var firstClone = this.runtime.getSpriteTargetByName(spriteName);
@@ -550,7 +550,7 @@ RenderedTarget.prototype.isTouchingSprite = function (spriteName) {
 /**
  * Return whether touching a color.
  * @param {Array.<number>} rgb [r,g,b], values between 0-255.
- * @return {Promise.<Boolean>} True iff the rendered target is touching the color.
+ * @return {Promise.<boolean>} True iff the rendered target is touching the color.
  */
 RenderedTarget.prototype.isTouchingColor = function (rgb) {
     if (this.renderer) {
@@ -561,9 +561,9 @@ RenderedTarget.prototype.isTouchingColor = function (rgb) {
 
 /**
  * Return whether rendered target's color is touching a color.
- * @param {Object} targetRgb {Array.<number>} [r,g,b], values between 0-255.
- * @param {Object} maskRgb {Array.<number>} [r,g,b], values between 0-255.
- * @return {Promise.<Boolean>} True iff the color is touching the color.
+ * @param {object} targetRgb {Array.<number>} [r,g,b], values between 0-255.
+ * @param {object} maskRgb {Array.<number>} [r,g,b], values between 0-255.
+ * @return {Promise.<boolean>} True iff the color is touching the color.
  */
 RenderedTarget.prototype.colorIsTouchingColor = function (targetRgb, maskRgb) {
     if (this.renderer) {
@@ -611,7 +611,7 @@ RenderedTarget.prototype.goBehindOther = function (other) {
  * Keep a desired position within a fence.
  * @param {number} newX New desired X position.
  * @param {number} newY New desired Y position.
- * @param {Object=} optFence Optional fence with left, right, top bottom.
+ * @param {object=} optFence Optional fence with left, right, top bottom.
  * @return {Array.<number>} Fenced X and Y coordinates.
  */
 RenderedTarget.prototype.keepInFence = function (newX, newY, optFence) {
diff --git a/src/util/cast.js b/src/util/cast.js
index 0723b5ecd..a8a1535b8 100644
--- a/src/util/cast.js
+++ b/src/util/cast.js
@@ -95,7 +95,7 @@ Cast.toRgbColorObject = function (value) {
  * In Scratch 2.0, this is captured by `interp.compare.`
  * @param {*} v1 First value to compare.
  * @param {*} v2 Second value to compare.
- * @returns {Number} Negative number if v1 < v2; 0 if equal; positive otherwise.
+ * @returns {number} Negative number if v1 < v2; 0 if equal; positive otherwise.
  */
 Cast.compare = function (v1, v2) {
     var n1 = Number(v1);
diff --git a/src/virtual-machine.js b/src/virtual-machine.js
index 8e9b4a940..003c80e9f 100644
--- a/src/virtual-machine.js
+++ b/src/virtual-machine.js
@@ -75,7 +75,7 @@ VirtualMachine.prototype.greenFlag = function () {
 /**
  * Set whether the VM is in "turbo mode."
  * When true, loops don't yield to redraw.
- * @param {Boolean} turboModeOn Whether turbo mode should be set.
+ * @param {boolean} turboModeOn Whether turbo mode should be set.
  */
 VirtualMachine.prototype.setTurboMode = function (turboModeOn) {
     this.runtime.turboMode = !!turboModeOn;
@@ -84,7 +84,7 @@ VirtualMachine.prototype.setTurboMode = function (turboModeOn) {
 /**
  * Set whether the VM is in 2.0 "compatibility mode."
  * When true, ticks go at 2.0 speed (30 TPS).
- * @param {Boolean} compatibilityModeOn Whether compatibility mode is set.
+ * @param {boolean} compatibilityModeOn Whether compatibility mode is set.
  */
 VirtualMachine.prototype.setCompatibilityMode = function (compatibilityModeOn) {
     this.runtime.setCompatibilityMode(!!compatibilityModeOn);
@@ -129,7 +129,7 @@ VirtualMachine.prototype.getPlaygroundData = function () {
 /**
  * Post I/O data to the virtual devices.
  * @param {?string} device Name of virtual I/O device.
- * @param {Object} data Any data object to post to the I/O device.
+ * @param {object} data Any data object to post to the I/O device.
  */
 VirtualMachine.prototype.postIOData = function (device, data) {
     if (this.runtime.ioDevices[device]) {
@@ -168,7 +168,7 @@ VirtualMachine.prototype.addSprite2 = function (json) {
 
 /**
  * Add a costume to the current editing target.
- * @param {!Object} costumeObject Object representing the costume.
+ * @param {!object} costumeObject Object representing the costume.
  */
 VirtualMachine.prototype.addCostume = function (costumeObject) {
     this.editingTarget.sprite.costumes.push(costumeObject);
@@ -180,7 +180,7 @@ VirtualMachine.prototype.addCostume = function (costumeObject) {
 
 /**
  * Add a backdrop to the stage.
- * @param {!Object} backdropObject Object representing the backdrop.
+ * @param {!object} backdropObject Object representing the backdrop.
  */
 VirtualMachine.prototype.addBackdrop = function (backdropObject) {
     var stage = this.runtime.getTargetForStage();