diff --git a/src/engine/runtime.js b/src/engine/runtime.js
index a8bd98c5..6e4c0c87 100644
--- a/src/engine/runtime.js
+++ b/src/engine/runtime.js
@@ -83,6 +83,12 @@ var Runtime = function () {
      */
     this._scriptGlowsPreviousFrame = [];
 
+    /**
+     * Number of threads running during the previous frame
+     * @type {number}
+     */
+    this._threadCount = 0;
+
     /**
      * Currently known number of clones, used to enforce clone limit.
      * @type {number}
@@ -179,6 +185,18 @@ Runtime.BLOCK_GLOW_ON = 'BLOCK_GLOW_ON';
  */
 Runtime.BLOCK_GLOW_OFF = 'BLOCK_GLOW_OFF';
 
+/**
+ * Event name for glowing the green flag
+ * @const {string}
+ */
+Runtime.PROJECT_RUN_START = 'PROJECT_RUN_START'
+
+/**
+ * Event name for unglowing the green flag
+ * @const {string}
+ */
+Runtime.PROJECT_RUN_STOP = 'PROJECT_RUN_STOP'
+
 /**
  * Event name for visual value report.
  * @const {string}
@@ -552,6 +570,7 @@ Runtime.prototype._step = function () {
     this.redrawRequested = false;
     var inactiveThreads = this.sequencer.stepThreads();
     this._updateGlows(inactiveThreads);
+    this._setThreadCount(this.threads.length);
     if (this.renderer) {
         // @todo: Only render when this.redrawRequested or clones rendered.
         this.renderer.draw();
@@ -639,6 +658,20 @@ Runtime.prototype._updateGlows = function (optExtraThreads) {
     this._scriptGlowsPreviousFrame = finalScriptGlows;
 };
 
+/**
+ * Emit run start/stop after each tick. Emits when `this.threads.length` goes
+ * between non-zero and zero
+ */
+Runtime.prototype._setThreadCount = function (threadCount) {
+    if (this._threadCount === 0 && threadCount > 0) {
+        this.emit(Runtime.PROJECT_RUN_START);
+    }
+    if (this._threadCount > 0 && threadCount === 0) {
+        this.emit(Runtime.PROJECT_RUN_STOP);
+    }
+    this._threadCount = threadCount;
+};
+
 /**
  * "Quiet" a script's glow: stop the VM from generating glow/unglow events
  * about that script. Use when a script has just been deleted, but we may
diff --git a/src/index.js b/src/index.js
index 8b390f35..4ed724f3 100644
--- a/src/index.js
+++ b/src/index.js
@@ -37,6 +37,11 @@ var VirtualMachine = function () {
     instance.runtime.on(Runtime.BLOCK_GLOW_OFF, function (glowData) {
         instance.emit(Runtime.BLOCK_GLOW_OFF, glowData);
     });
+    instance.runtime.on(Runtime.PROJECT_RUN_START, function () {
+        instance.emit(Runtime.PROJECT_RUN_START);
+    });
+    instance.runtime.on(Runtime.PROJECT_RUN_STOP, function () {
+        instance.emit(Runtime.PROJECT_RUN_STOP);
     });
     instance.runtime.on(Runtime.VISUAL_REPORT, function (visualReport) {
         instance.emit(Runtime.VISUAL_REPORT, visualReport);