diff --git a/docs/how-to-create-new-effects.md b/docs/how-to-create-new-effects.md
index 3296cfe..a2a1f30 100644
--- a/docs/how-to-create-new-effects.md
+++ b/docs/how-to-create-new-effects.md
@@ -121,7 +121,8 @@ var SimpleFade = class SimpleFade {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'simple-fade';
   }
@@ -148,24 +149,12 @@ var SimpleFade = class SimpleFade {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('simple-fade-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // We re-target these transitions so that the window is neither scaled nor faded.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1);
-    tweakTransition('scale-y', 1);
+  // GNOME Shell. For each property, you can set a "from", "to", and a "mode". For this
+  // effect, windows should neither be scaled nor faded.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 1.0}, 'scale-y': {to: 1.0}};
   }
 }
 
diff --git a/extension.js b/extension.js
index 74909df..b4de8ae 100644
--- a/extension.js
+++ b/extension.js
@@ -66,6 +66,10 @@ class Extension {
     // Store a reference to the settings object.
     this._settings = ExtensionUtils.getSettings();
 
+    // This will store an item of ALL_EFFECTS which was used the last time a window was
+    // closed.
+    this._effect = 0;
+
     // We will monkey-patch these three methods. Let's store the original ones.
     this._origWindowRemoved      = Workspace.prototype._windowRemoved;
     this._origDoRemoveWindow     = Workspace.prototype._doRemoveWindow;
@@ -87,7 +91,20 @@ class Extension {
 
       WindowPreview.prototype._deleteAll = function() {
         if (!this._closeRequested) {
+
+          this.metaWindow.connect('unmanaged', () => {
+            const transitionConfig = extensionThis._effect.getCloseTransition(
+                this.window_container, extensionThis._settings);
+            extensionThis._tweakTransitions(this.window_container, transitionConfig);
+          });
+
           extensionThis._origDeleteAll.apply(this);
+
+          // This is required, else WindowPreview's _restack() which is called by the
+          // "this.overlayEnabled = false", sometimes tries to access an already delete
+          // WindowPreview.
+          this._stackAbove    = null;
+          this.overlayEnabled = false;
         }
       };
     }
@@ -175,13 +192,14 @@ class Extension {
       }
 
       // Choose a random effect.
-      const Effect = enabledEffects[Math.floor(Math.random() * enabledEffects.length)];
+      this._effect = enabledEffects[Math.floor(Math.random() * enabledEffects.length)];
 
       // The effect usually will choose to override the present transitions on the actor.
-      Effect.tweakTransitions(actor, this._settings);
+      const transitionConfig = this._effect.getCloseTransition(actor, this._settings);
+      this._tweakTransitions(actor, transitionConfig);
 
       // Add a cool shader to our window actor!
-      const shader = Effect.createShader(actor, this._settings);
+      const shader = this._effect.createShader(actor, this._settings);
 
       if (shader) {
         actor.add_effect(shader);
@@ -255,6 +273,42 @@ class Extension {
 
     return false;
   }
+
+  // This is used to tweak the ongoing transitions of a window actor. This is either the
+  // actual actor of the Meta.Window or a clone in the overview. Usually windows are faded
+  // to transparency and scaled down slightly by GNOME Shell. Here, we allow modifications
+  // to this behavior by the effects.
+  _tweakTransitions(actor, config) {
+    const duration = this._settings.get_int(this._effect.getNick() + '-animation-time');
+
+    for (const property in config) {
+      const from = config[property].from;
+      const to   = config[property].to;
+      const mode = config[property].mode;
+
+      const transition = actor.get_transition(property);
+
+      if (transition) {
+        transition.set_duration(duration);
+
+        if (to != undefined) transition.set_to(to);
+        if (from != undefined) transition.set_from(from);
+        if (mode != undefined) transition.set_progress_mode(mode);
+
+      } else {
+
+        if (from != undefined) actor[property] = from;
+
+        if (to != undefined) {
+          actor.save_easing_state();
+          actor.set_easing_duration(duration)
+          if (mode != undefined) actor.set_easing_mode(mode);
+          actor[property] = to;
+          actor.restore_easing_state();
+        }
+      }
+    }
+  }
 }
 
 // This function is called once when the extension is loaded, not enabled.
diff --git a/src/EnergizeA.js b/src/EnergizeA.js
index b20be00..c1c0913 100644
--- a/src/EnergizeA.js
+++ b/src/EnergizeA.js
@@ -40,7 +40,8 @@ var EnergizeA = class EnergizeA {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'energize-a';
   }
@@ -80,24 +81,11 @@ var EnergizeA = class EnergizeA {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('energize-a-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // We re-target these transitions so that the window is neither scaled nor faded.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1);
-    tweakTransition('scale-y', 1);
+  // GNOME Shell. For this effect, windows should neither be scaled nor faded.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 1.0}, 'scale-y': {to: 1.0}};
   }
 }
 
diff --git a/src/EnergizeB.js b/src/EnergizeB.js
index 0bf87d8..afb6365 100644
--- a/src/EnergizeB.js
+++ b/src/EnergizeB.js
@@ -40,7 +40,8 @@ var EnergizeB = class EnergizeB {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'energize-b';
   }
@@ -80,24 +81,11 @@ var EnergizeB = class EnergizeB {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('energize-b-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // We re-target these transitions so that the window is neither scaled nor faded.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1);
-    tweakTransition('scale-y', 1);
+  // GNOME Shell. For this effect, windows should neither be scaled nor faded.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 1.0}, 'scale-y': {to: 1.0}};
   }
 }
 
diff --git a/src/Fire.js b/src/Fire.js
index 5060b5e..2cf1b44 100644
--- a/src/Fire.js
+++ b/src/Fire.js
@@ -44,7 +44,8 @@ var Fire = class Fire {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'fire';
   }
@@ -101,24 +102,11 @@ var Fire = class Fire {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('fire-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // We re-target these transitions so that the window is neither scaled nor faded.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1);
-    tweakTransition('scale-y', 1);
+  // GNOME Shell. For this effect, windows should neither be scaled nor faded.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 1.0}, 'scale-y': {to: 1.0}};
   }
 
   // ----------------------------------------------------------------------- private stuff
diff --git a/src/Matrix.js b/src/Matrix.js
index 8d8ab66..9ae7dad 100644
--- a/src/Matrix.js
+++ b/src/Matrix.js
@@ -44,7 +44,8 @@ var Matrix = class Matrix {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'matrix';
   }
@@ -86,24 +87,11 @@ var Matrix = class Matrix {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('matrix-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // We re-target these transitions so that the window is neither scaled nor faded.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1);
-    tweakTransition('scale-y', 1);
+  // GNOME Shell. For this effect, windows should neither be scaled nor faded.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 1.0}, 'scale-y': {to: 1.0}};
   }
 }
 
diff --git a/src/TRexAttack.js b/src/TRexAttack.js
index 2c57293..5c8a478 100644
--- a/src/TRexAttack.js
+++ b/src/TRexAttack.js
@@ -42,7 +42,8 @@ var TRexAttack = class TRexAttack {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'trex';
   }
@@ -84,26 +85,17 @@ var TRexAttack = class TRexAttack {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('trex-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // For this effect, we slightly increase the window's scale as part of the warp
-    // effect.
+  // GNOME Shell. For this effect, we slightly increase the window's scale as part of the
+  // warp effect.
+  static getCloseTransition(actor, settings) {
     const warp = 0.5 * settings.get_double('claw-scratch-warp');
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1.0 + warp);
-    tweakTransition('scale-y', 1.0 + warp);
+    return {
+      'opacity': {to: 255},
+      'scale-x': {to: 1.0 + warp},
+      'scale-y': {to: 1.0 + warp}
+    };
   }
 }
 
diff --git a/src/TVEffect.js b/src/TVEffect.js
index 0d37efc..12bd8e9 100644
--- a/src/TVEffect.js
+++ b/src/TVEffect.js
@@ -42,7 +42,8 @@ var TVEffect = class TVEffect {
 
   // This will be called in various places where a unique identifier for this effect is
   // required. It should match the prefix of the settings keys which store whether the
-  // effect is enabled currently (e.g. the '*-close-effect').
+  // effect is enabled currently (e.g. '*-close-effect'), and its animation time
+  // (e.g. '*-animation-time').
   static getNick() {
     return 'tv';
   }
@@ -81,24 +82,11 @@ var TVEffect = class TVEffect {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('tv-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // For this effect, we scale the window only vertically.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 1);
-    tweakTransition('scale-y', 0.5);
+  // GNOME Shell. For this effect, windows are scaled down vertically.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 1.0}, 'scale-y': {to: 0.5}};
   }
 }
 
diff --git a/src/Wisps.js b/src/Wisps.js
index e73b29a..87d6e2a 100644
--- a/src/Wisps.js
+++ b/src/Wisps.js
@@ -27,9 +27,10 @@ const utils          = Me.imports.src.utils;
 // The shader class for this effect is registered further down in this file.
 let Shader = null;
 
-// The effect class is completely static. It can be used to get some metadata (like the
-// effect's name or supported GNOME Shell versions), to initialize the respective page of
-// the settings dialog, as well as to create the actual shader for the effect.
+// This will be called in various places where a unique identifier for this effect is
+// required. It should match the prefix of the settings keys which store whether the
+// effect is enabled currently (e.g. '*-close-effect'), and its animation time
+// (e.g. '*-animation-time').
 var Wisps = class Wisps {
 
   // ---------------------------------------------------------------------------- metadata
@@ -80,25 +81,11 @@ var Wisps = class Wisps {
     return new Shader(settings);
   }
 
-  // This is also called from extension.js. It is used to tweak the ongoing transitions of
+  // This is also called from extension.js. It is used to tweak the ongoing transition of
   // the actor - usually windows are faded to transparency and scaled down slightly by
-  // GNOME Shell. Here, we modify this behavior as well as the transition duration.
-  static tweakTransitions(actor, settings) {
-    const animationTime = settings.get_int('wisps-animation-time');
-
-    const tweakTransition = (property, value) => {
-      const transition = actor.get_transition(property);
-      if (transition) {
-        transition.set_to(value);
-        transition.set_duration(animationTime);
-      }
-    };
-
-    // We re-target these transitions so that the window is not faded but scaled down a
-    // tiny bit.
-    tweakTransition('opacity', 255);
-    tweakTransition('scale-x', 0.9);
-    tweakTransition('scale-y', 0.9);
+  // GNOME Shell. For this effect, windows should be scaled down slightly but not faded.
+  static getCloseTransition(actor, settings) {
+    return {'opacity': {to: 255}, 'scale-x': {to: 0.9}, 'scale-y': {to: 0.9}};
   }
 }