diff --git a/nannou/Cargo.toml b/nannou/Cargo.toml
index 3d50152bf..adc1c109e 100644
--- a/nannou/Cargo.toml
+++ b/nannou/Cargo.toml
@@ -29,6 +29,7 @@ serde = "1"
 serde_derive = "1"
 serde_json = "1"
 toml = "0.5"
+trait-set = "0.3.0"
 walkdir = "2"
 web-sys = { version = "0.3.55", optional = true }
 wgpu_upstream = { version = "0.11.1", package = "wgpu" }
diff --git a/nannou/src/app.rs b/nannou/src/app.rs
index 6fd899182..9a165e891 100644
--- a/nannou/src/app.rs
+++ b/nannou/src/app.rs
@@ -27,43 +27,46 @@ use std::sync::atomic::{self, AtomicBool};
 use std::sync::Arc;
 use std::time::Duration;
 use std::{self, future};
+use trait_set::trait_set;
 use winit;
 use winit::event_loop::ControlFlow;
 
-/// The user function type for initialising their model.
-pub type ModelFn<Model> = fn(&App) -> Model;
+trait_set! {
+    /// The user function type for initialising their model.
+    pub trait ModelFn<Model> = 'static + Fn(&App) -> Model;
 
-/// The user function type for updating their model in accordance with some event.
-pub type EventFn<Model, Event> = fn(&App, &mut Model, Event);
+    /// The user function type for updating their model in accordance with some event.
+    pub trait EventFn<Model, Event> = 'static + Fn(&App, &mut Model, Event);
 
-/// The user function type for updating the user model within the application loop.
-pub type UpdateFn<Model> = fn(&App, &mut Model, Update);
+    /// The user function type for updating the user model within the application loop.
+    pub trait UpdateFn<Model> = 'static + Fn(&App, &mut Model, Update);
 
-/// The user function type for drawing their model to the surface of a single window.
-pub type ViewFn<Model> = fn(&App, &Model, Frame);
+    /// The user function type for drawing their model to the surface of a single window.
+    pub trait ViewFn<Model> = 'static + Fn(&App, &Model, Frame);
 
-/// A shorthand version of `ViewFn` for sketches where the user does not need a model.
-pub type SketchViewFn = fn(&App, Frame);
+    /// A shorthand version of `ViewFn` for sketches where the user does not need a model.
+    pub trait SketchViewFn = 'static + Fn(&App, Frame);
 
-/// The user function type allowing them to consume the `model` when the application exits.
-pub type ExitFn<Model> = fn(&App, Model);
+    /// The user function type allowing them to consume the `model` when the application exits.
+    pub trait ExitFn<Model> = 'static + Fn(&App, Model);
+}
 
 /// The **App**'s view function.
 enum View<Model = ()> {
     /// A view function allows for viewing the user's model.
-    WithModel(ViewFn<Model>),
+    WithModel(Box<dyn ViewFn<Model>>),
     /// A **Simple** view function does not require a user **Model**. Simpler to get started.
-    Sketch(SketchViewFn),
+    Sketch(Box<dyn SketchViewFn>),
 }
 
 /// A nannou `App` builder.
 pub struct Builder<M = (), E = Event> {
     model: Box<dyn FnOnce(&App) -> Box<dyn Future<Output = M> + '_>>,
     config: Config,
-    event: Option<EventFn<M, E>>,
-    update: Option<UpdateFn<M>>,
+    event: Option<Box<dyn EventFn<M, E>>>,
+    update: Option<Box<dyn UpdateFn<M>>>,
     default_view: Option<View<M>>,
-    exit: Option<ExitFn<M>>,
+    exit: Option<Box<dyn ExitFn<M>>>,
     create_default_window: bool,
     default_window_size: Option<DefaultWindowSize>,
     capture_frame_timeout: Option<Option<Duration>>,
@@ -251,7 +254,7 @@ where
     ///
     /// The Model that is returned by the function is the same model that will be passed to the
     /// given event and view functions.
-    pub fn new(model: ModelFn<M>) -> Self {
+    pub fn new(model: impl ModelFn<M>) -> Self {
         Self::new_async(move |app| Box::new(future::ready(model(app))))
     }
 
@@ -281,7 +284,7 @@ where
     /// occur during the life of the program. These include things like `Update`s and
     /// `WindowEvent`s such as `KeyPressed`, `MouseMoved`, and so on.
     #[cfg_attr(rustfmt, rustfmt_skip)]
-    pub fn event<E>(self, event: EventFn<M, E>) -> Builder<M, E>
+    pub fn event<E>(self, event: impl EventFn<M, E>) -> Builder<M, E>
     where
         E: LoopEvent,
     {
@@ -301,7 +304,7 @@ where
         Builder {
             model,
             config,
-            event: Some(event),
+            event: Some(Box::new(event)),
             update,
             default_view,
             exit,
@@ -332,8 +335,8 @@ where
     ///
     /// Note that when working with more than one window, you can use `frame.window_id()` to
     /// determine which window the current call is associated with.
-    pub fn view(mut self, view: ViewFn<M>) -> Self {
-        self.default_view = Some(View::WithModel(view));
+    pub fn view(mut self, view: impl ViewFn<M>) -> Self {
+        self.default_view = Some(View::WithModel(Box::new(view)));
         self
     }
 
@@ -345,8 +348,8 @@ where
     /// Update events are also emitted as a variant of the `event` function. Note that if you
     /// specify both an `event` function and an `update` function, the `event` function will always
     /// be called with an update event prior to this `update` function.
-    pub fn update(mut self, update: UpdateFn<M>) -> Self {
-        self.update = Some(update);
+    pub fn update(mut self, update: impl UpdateFn<M>) -> Self {
+        self.update = Some(Box::new(update));
         self
     }
 
@@ -363,8 +366,8 @@ where
     /// `App::new_window` method. The role of this `simple_window` method is to provide a
     /// quick-and-easy way to start with a simple window. This can be very useful for quick ideas,
     /// small single-window applications and examples.
-    pub fn simple_window(mut self, view: ViewFn<M>) -> Self {
-        self.default_view = Some(View::WithModel(view));
+    pub fn simple_window(mut self, view: impl ViewFn<M>) -> Self {
+        self.default_view = Some(View::WithModel(Box::new(view)));
         self.create_default_window = true;
         self
     }
@@ -373,8 +376,8 @@ where
     ///
     /// The exit function gives ownership of the model back to you for any cleanup that might be
     /// necessary.
-    pub fn exit(mut self, exit: ExitFn<M>) -> Self {
-        self.exit = Some(exit);
+    pub fn exit(mut self, exit: impl ExitFn<M>) -> Self {
+        self.exit = Some(Box::new(exit));
         self
     }
 
@@ -547,9 +550,9 @@ impl Builder<(), Event> {
     ///
     /// This is useful for late night hack sessions where you just don't care about all that other
     /// stuff, you just want to play around with some ideas or make something pretty.
-    pub fn sketch(view: SketchViewFn) -> SketchBuilder<Event> {
+    pub fn sketch(view: impl SketchViewFn) -> SketchBuilder<Event> {
         let mut builder = Builder::new(default_model);
-        builder.default_view = Some(View::Sketch(view));
+        builder.default_view = Some(View::Sketch(Box::new(view)));
         builder.create_default_window = true;
         SketchBuilder { builder }
     }
@@ -1028,7 +1031,7 @@ impl EventLoopWindowTarget {
     // This method is solely used during `window::Builder::build` to allow for
     pub(crate) fn as_ref(&self) -> &winit::event_loop::EventLoopWindowTarget<()> {
         match *self {
-            EventLoopWindowTarget::Owned(ref event_loop) => (&**event_loop),
+            EventLoopWindowTarget::Owned(ref event_loop) => &**event_loop,
             EventLoopWindowTarget::Pointer(ptr) => {
                 // This cast is safe, assuming that the `App`'s `EventLoopWindowTarget` will only
                 // ever be in the `Pointer` state while the pointer is valid - that is, during the
@@ -1056,10 +1059,10 @@ impl EventLoopWindowTarget {
 fn run_loop<M, E>(
     mut app: App,
     model: M,
-    event_fn: Option<EventFn<M, E>>,
-    update_fn: Option<UpdateFn<M>>,
+    event_fn: Option<impl EventFn<M, E>>,
+    update_fn: Option<impl UpdateFn<M>>,
     default_view: Option<View<M>>,
-    exit_fn: Option<ExitFn<M>>,
+    exit_fn: Option<impl ExitFn<M>>,
 ) where
     M: 'static,
     E: LoopEvent,
@@ -1100,9 +1103,6 @@ fn run_loop<M, E>(
                 if let Some(model) = model.as_mut() {
                     let loop_mode = app.loop_mode();
                     let now = Instant::now();
-                    let mut do_update = |loop_state: &mut LoopState| {
-                        apply_update(&mut app, model, event_fn, update_fn, loop_state, now);
-                    };
                     match loop_mode {
                         LoopMode::NTimes { number_of_updates }
                             if loop_state.total_updates >= number_of_updates as u64 => {}
@@ -1114,7 +1114,7 @@ fn run_loop<M, E>(
                         // LoopMode::Wait { updates_before_waiting } =>
                         //     if loop_state.updates_since_event > updates_before_waiting as u64 => {}
                         _ => {
-                            do_update(&mut loop_state);
+                            apply_update(&mut app, model, &event_fn, &update_fn, &mut loop_state, now);
                         },
                     }
                 }
@@ -1231,13 +1231,13 @@ fn run_loop<M, E>(
                                 (*raw_view)(&app, &model, raw_frame);
                             }
                             None => match default_view {
-                                Some(View::Sketch(view)) => {
+                                Some(View::Sketch(ref view)) => {
                                     let data = frame_data.as_ref().expect("missing `frame_data`");
                                     let frame =
                                         Frame::new_empty(raw_frame, &data.render, &data.capture);
                                     view(&app, frame);
                                 }
-                                Some(View::WithModel(view)) => {
+                                Some(View::WithModel(ref view)) => {
                                     let data = frame_data.as_ref().expect("missing `frame_data`");
                                     let frame =
                                         Frame::new_empty(raw_frame, &data.render, &data.capture);
@@ -1330,7 +1330,7 @@ fn run_loop<M, E>(
 
         // Process the event with the user's functions and see if we need to exit.
         if let Some(model) = model.as_mut() {
-            exit |= process_and_emit_winit_event::<M, E>(&mut app, model, event_fn, &event);
+            exit |= process_and_emit_winit_event::<M, E>(&mut app, model, &event_fn, &event);
         }
 
         // Set the control flow based on the loop mode.
@@ -1348,7 +1348,7 @@ fn run_loop<M, E>(
         // If we need to exit, call the user's function and update control flow.
         if exit {
             if let Some(model) = model.take() {
-                if let Some(exit_fn) = exit_fn {
+                if let Some(exit_fn) = exit_fn.as_ref() {
                     exit_fn(&app, model);
                 }
             }
@@ -1372,8 +1372,8 @@ fn run_loop<M, E>(
 fn apply_update<M, E>(
     app: &mut App,
     model: &mut M,
-    event_fn: Option<EventFn<M, E>>,
-    update_fn: Option<UpdateFn<M>>,
+    event_fn: &Option<impl EventFn<M, E>>,
+    update_fn: &Option<impl UpdateFn<M>>,
     loop_state: &mut LoopState,
     now: Instant,
 ) where
@@ -1458,7 +1458,7 @@ fn should_toggle_fullscreen(
 fn process_and_emit_winit_event<'a, M, E>(
     app: &mut App,
     model: &mut M,
-    event_fn: Option<EventFn<M, E>>,
+    event_fn: &Option<impl EventFn<M, E>>,
     winit_event: &winit::event::Event<'a, ()>,
 ) -> bool
 where
diff --git a/nannou/src/lib.rs b/nannou/src/lib.rs
index f63e0f60e..78afb113d 100644
--- a/nannou/src/lib.rs
+++ b/nannou/src/lib.rs
@@ -54,7 +54,7 @@ pub mod window;
 ///
 /// The Model that is returned by the function is the same model that will be passed to the
 /// given event and view functions.
-pub fn app<M: 'static>(model: app::ModelFn<M>) -> app::Builder<M, Event> {
+pub fn app<M: 'static>(model: impl app::ModelFn<M>) -> app::Builder<M, Event> {
     app::Builder::new(model)
 }
 
@@ -63,6 +63,6 @@ pub fn app<M: 'static>(model: app::ModelFn<M>) -> app::Builder<M, Event> {
 ///
 /// This is useful for late night hack sessions where you just don't care about all that other
 /// stuff, you just want to play around with some ideas or make something pretty.
-pub fn sketch(view: app::SketchViewFn) -> app::SketchBuilder<Event> {
+pub fn sketch(view: impl app::SketchViewFn) -> app::SketchBuilder<Event> {
     app::Builder::sketch(view)
 }