diff --git a/input/input.rs b/input/input.rs
index 2695a47..5a22800 100644
--- a/input/input.rs
+++ b/input/input.rs
@@ -26,8 +26,8 @@ flex_trait_mut!(Handle <E: Input> {
 });
 
 pub trait Command<S>: Send + Sync + Sized {
-    fn execute (self, state: &mut S) -> Perhaps<Self>;
-    fn delegate <T> (self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
+    fn execute (&self, state: &mut S) -> Perhaps<Self>;
+    fn delegate <T> (&self, state: &mut S, wrap: impl Fn(Self)->T) -> Perhaps<T>
         where Self: Sized
     {
         Ok(self.execute(state)?.map(wrap))
@@ -35,10 +35,10 @@ pub trait Command<S>: Send + Sync + Sized {
 }
 
 impl<S, T: Command<S>> Command<S> for Option<T> {
-    fn execute (self, _: &mut S) -> Perhaps<Self> {
+    fn execute (&self, _: &mut S) -> Perhaps<Self> {
         Ok(None)
     }
-    fn delegate <U> (self, _: &mut S, _: impl Fn(Self)->U) -> Perhaps<U>
+    fn delegate <U> (&self, _: &mut S, _: impl Fn(Self)->U) -> Perhaps<U>
         where Self: Sized
     {
         Ok(None)
@@ -49,13 +49,30 @@ impl<S, T: Command<S>> Command<S> for Option<T> {
 #[macro_export] macro_rules! command {
     ($(<$($l:lifetime),+>)?|$self:ident:$Command:ty,$state:ident:$State:ty|$handler:expr) => {
         impl$(<$($l),+>)? ::tengri::input::Command<$State> for $Command {
-            fn execute ($self, $state: &mut $State) -> Perhaps<Self> {
+            fn execute (&$self, $state: &mut $State) -> Perhaps<Self> {
                 Ok($handler)
             }
         }
     };
 }
 
+#[macro_export] macro_rules! def_command (($Command:ident: |$state:ident: $State:ty| {
+    $($Variant:ident$({$($arg:ident:$Arg:ty),+ $(,)?})?=>$body:expr),* $(,)?
+})=>{
+    #[derive(Debug)]
+    pub enum $Command {
+        $($Variant $({ $($arg: $Arg),* })?),*
+    }
+    impl Command<$State> for $Command {
+        fn execute (&self, $state: &mut $State) -> Perhaps<Self> {
+            match self {
+                $(Self::$Variant $({ $($arg),* })? => $body,)*
+                _ => unimplemented!("Command<{}>: {self:?}", stringify!($State)),
+            }
+        }
+    }
+});
+
 /// Implement [Handle] for given `State` and `handler`.
 #[macro_export] macro_rules! handle {
     (|$self:ident:$State:ty,$input:ident|$handler:expr) => {