diff --git a/Makefile b/Makefile
index 0bf8477..4a46cca 100644
--- a/Makefile
+++ b/Makefile
@@ -12,7 +12,7 @@ test:
 
 .PHONY: run
 run:
-	cargo run -- game.ayin
+	RUST_BACKTRACE=1 cargo run -- game.ayin
 
 .PHONY: review
 review:
diff --git a/game.ayin b/game.ayin
index 5790989..b771c25 100644
--- a/game.ayin
+++ b/game.ayin
@@ -10,8 +10,8 @@ let update = fn(state, input) {
   return state;
 };
 
-let draw = fn(frame, state) {
-  frame.clear(0,0,0);
+let draw = fn(state) {
+  frame_clear(0,0,0);
 };
 
 let migrate = fn(state) {
diff --git a/src/ast/types.rs b/src/ast/types.rs
index 05690ab..c577e47 100644
--- a/src/ast/types.rs
+++ b/src/ast/types.rs
@@ -71,6 +71,7 @@ pub enum Value {
     Label(Label),
     Ref(Ref),
     Closure { env: EnvName, expr: Box<Expr> },
+    PrimitiveFunc(Name),
 }
 
 /// A mutable variable.
@@ -91,7 +92,7 @@ pub struct Arg {
 }
 
 /// A symbol.
-#[derive(PartialEq, Eq, PartialOrd, Ord, Debug, Clone)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone)]
 pub struct Name(pub String);
 
 /// A field.
diff --git a/src/interpret/interpret.rs b/src/interpret/interpret.rs
index b2ca6c5..19a2606 100644
--- a/src/interpret/interpret.rs
+++ b/src/interpret/interpret.rs
@@ -1,6 +1,7 @@
 //! Interpreter for Ayin.
 
 use super::types::*;
+use std::backtrace::Backtrace;
 use std::collections::BTreeMap;
 
 use crate::ast;
@@ -9,8 +10,8 @@ pub fn global_env_name() -> ast::EnvName {
     ast::EnvName("global".to_string())
 }
 
-pub fn setup(program: ast::Program) -> Result<State, Error> {
-    let mut state = State::new(global_env_name().0.clone());
+pub fn setup(program: ast::Program, prim_funcs: PrimitiveFuncs) -> Result<State, Error> {
+    let mut state = State::new(global_env_name().0.clone(), prim_funcs);
 
     defs_to_env(program.0, &global_env_name(), &mut state)?;
     Ok(state)
@@ -39,7 +40,7 @@ pub fn run(
     func: ast::Name,
     args: Vec<ast::Expr>,
 ) -> Result<ast::Value, Error> {
-    let mut state = setup(program)?;
+    let mut state = setup(program, PrimitiveFuncs::new(vec![]))?;
     interpret(&mut state, func, args)
 }
 
@@ -89,7 +90,7 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
                     eval_expr(expr_env, state, r#else)
                 }
             }
-            v => Err(Error::NotABoolean(v)),
+            v => Err(Error::NotABoolean(v, Backtrace::capture())),
         },
         ast::Expr::Func(func) => {
             let env_name = state.generate_env(expr_env.clone())?;
@@ -113,12 +114,12 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
             })? {
                 Ok(last)
             } else {
-                Err(Error::LastStatementNotAnExpr)
+                Err(Error::LastStatementNotAnExpr(Backtrace::capture()))
             }
         }
         ast::Expr::Access { expr, field } => match eval_expr(expr_env, state, expr)? {
             ast::Value::Record(record) => Ok(state.variables.get(record.get(&field)?).clone()),
-            v => Err(Error::NotARecord(v)),
+            v => Err(Error::NotARecord(v, Backtrace::capture())),
         },
         ast::Expr::Var(var) => {
             let value = expr_env.get(var)?.clone();
@@ -131,7 +132,7 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
                     let mut closure_env: Env = state.envs.get(&env)?.clone();
 
                     if func.args.len() != args.len() {
-                        Err(Error::ArgumentsMismatch)?;
+                        Err(Error::ArgumentsMismatch(Backtrace::capture()))?;
                     }
 
                     for (arg, e) in func.args.into_iter().zip(args.iter()) {
@@ -140,9 +141,27 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
                     }
                     eval_expr(&closure_env, state, &func.body)
                 }
-                e => Err(Error::NotAFunction(e)),
+                e => Err(Error::NotAFunction(e, Backtrace::capture())),
             },
-            e => Err(Error::NotAFunction(ast::Expr::Value(e))),
+            ast::Value::PrimitiveFunc(func) => {
+                let mut argsvec = vec![];
+                for arg in args.iter() {
+                    let evalled = eval_expr(&expr_env, state, arg)?;
+                    argsvec.push(evalled);
+                }
+                if let Some(func) = state.primitive_funcs.get(&func) {
+                    Ok(func(argsvec))
+                } else {
+                    Err(Error::NotAFunction(
+                        ast::Expr::Value(ast::Value::PrimitiveFunc(func)),
+                        Backtrace::capture(),
+                    ))
+                }
+            }
+            e => Err(Error::NotAFunction(
+                ast::Expr::Value(e),
+                Backtrace::capture(),
+            )),
         },
         ast::Expr::Value(v) => match v {
             ast::Value::Closure { expr, env } => {
@@ -159,7 +178,7 @@ fn eval_expr(expr_env: &Env, state: &mut State, expr: &ast::Expr) -> Result<ast:
                     state.variables.set(reference, rhs.clone());
                     Ok(rhs)
                 }
-                v => Err(Error::NotAReference(v.clone())),
+                v => Err(Error::NotAReference(v.clone(), Backtrace::capture())),
             },
             /*
             _ => {
@@ -200,12 +219,12 @@ fn eval_expr_shallow(
             let result = expr_env.get(&var)?;
             match result {
                 ast::Value::Ref(_) => Ok(result.clone()),
-                v => Err(Error::NotAReference(v.clone())),
+                v => Err(Error::NotAReference(v.clone(), Backtrace::capture())),
             }
         }
         ast::Expr::Access { expr, field } => match eval_expr(expr_env, state, expr)? {
             ast::Value::Record(record) => Ok(ast::Value::Ref(record.get(&field)?.clone())),
-            v => Err(Error::NotARecord(v)),
+            v => Err(Error::NotARecord(v, Backtrace::capture())),
         },
         _ => eval_expr(expr_env, state, expr),
     }
@@ -385,7 +404,10 @@ mod tests {
         ]
         .into();
         let result = run(program, "main".into(), vec![]);
-        assert_eq!(result, Err(Error::DuplicateNames("main".into())));
+        assert_eq!(
+            result,
+            Err(Error::DuplicateNames("main".into(), Backtrace::capture()))
+        );
     }
 
     #[test]
@@ -396,7 +418,10 @@ mod tests {
         ]
         .into();
         let result = run(program, "main".into(), vec![]);
-        assert_eq!(result, Err(Error::NotARecord(0.into())));
+        assert_eq!(
+            result,
+            Err(Error::NotARecord(0.into(), Backtrace::capture()))
+        );
     }
     #[test]
     fn fun_call_not_a_function() {
@@ -406,6 +431,9 @@ mod tests {
         ]
         .into();
         let result = run(program, "main".into(), vec![]);
-        assert_eq!(result, Err(Error::NotAFunction(0.into())));
+        assert_eq!(
+            result,
+            Err(Error::NotAFunction(0.into(), Backtrace::capture()))
+        );
     }
 }
diff --git a/src/interpret/types.rs b/src/interpret/types.rs
index 1d912ba..57e52c2 100644
--- a/src/interpret/types.rs
+++ b/src/interpret/types.rs
@@ -1,39 +1,73 @@
 //! Types used in the interpreter.
 
 use crate::ast;
+use std::backtrace::Backtrace;
 use std::collections::BTreeMap;
 use std::collections::HashMap;
 
-#[derive(PartialEq, Debug, thiserror::Error)]
+#[derive(Debug)]
 pub enum Error {
-    #[error("Closure generation failed. Duplicate env names: {0:?}")]
-    DuplicateEnvNames(ast::EnvName),
-    #[error("Duplicate names: {0:?}")]
-    DuplicateNames(ast::Name),
-    #[error("Name not found: {0:?}")]
-    NameNotFound(ast::Name),
-    #[error("Field not found: {0:?}")]
-    FieldNotFound(ast::Label),
-    #[error("Env not found: {0:?}")]
-    EnvNotFound(ast::EnvName),
-    #[error("Last statement is not an expression")]
-    LastStatementNotAnExpr,
-    #[error("Not a function {0:?}")]
-    NotAFunction(ast::Expr),
-    #[error("Not a record {0:?}")]
-    NotARecord(ast::Value),
-    #[error("Not a reference {0:?}")]
-    NotAReference(ast::Value),
-    #[error("Not a boolean {0:?}")]
-    NotABoolean(ast::Value),
-    #[error("Arguments mismatch")]
-    ArgumentsMismatch,
+    DuplicateEnvNames(ast::EnvName, Backtrace),
+    DuplicateNames(ast::Name, Backtrace),
+    NameNotFound(ast::Name, Backtrace),
+    FieldNotFound(ast::Label, Backtrace),
+    EnvNotFound(ast::EnvName, Backtrace),
+    LastStatementNotAnExpr(Backtrace),
+    NotAFunction(ast::Expr, Backtrace),
+    NotARecord(ast::Value, Backtrace),
+    NotAReference(ast::Value, Backtrace),
+    NotABoolean(ast::Value, Backtrace),
+    ArgumentsMismatch(Backtrace),
+}
+impl PartialEq for Error {
+    fn eq(&self, other: &Self) -> bool {
+        match (self, other) {
+            (Error::DuplicateEnvNames(a1, _), Error::DuplicateEnvNames(a2, _)) => a1 == a2,
+            (Error::DuplicateNames(a1, _), Error::DuplicateNames(a2, _)) => a1 == a2,
+            (Error::NameNotFound(a1, _), Error::NameNotFound(a2, _)) => a1 == a2,
+            (Error::FieldNotFound(a1, _), Error::FieldNotFound(a2, _)) => a1 == a2,
+            (Error::EnvNotFound(a1, _), Error::EnvNotFound(a2, _)) => a1 == a2,
+            (Error::LastStatementNotAnExpr(_), Error::LastStatementNotAnExpr(_)) => true,
+
+            (Error::NotAFunction(a1, _), Error::NotAFunction(a2, _)) => a1 == a2,
+            (Error::NotARecord(a1, _), Error::NotARecord(a2, _)) => a1 == a2,
+            (Error::NotAReference(a1, _), Error::NotAReference(a2, _)) => a1 == a2,
+            (Error::NotABoolean(a1, _), Error::NotABoolean(a2, _)) => a1 == a2,
+            (Error::ArgumentsMismatch(_), Error::ArgumentsMismatch(_)) => true,
+            _ => false,
+        }
+    }
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::DuplicateEnvNames(a, b) => {
+                write!(
+                    f,
+                    "Closure generation failed. Duplicate env names: {a:?}\n{b}"
+                )
+            }
+            Error::DuplicateNames(a, b) => write!(f, "Duplicate names: {a:?}\n{b}"),
+            Error::NameNotFound(a, b) => write!(f, "Name not found: {a:?}\n{b}"),
+            Error::FieldNotFound(a, b) => write!(f, "Field not found: {a:?}\n{b}"),
+            Error::EnvNotFound(a, b) => write!(f, "Env not found: {a:?}\n{b}"),
+            Error::LastStatementNotAnExpr(a) => {
+                write!(f, "Last statement is not an expression\n{a}")
+            }
+            Error::NotAFunction(a, b) => write!(f, "Not a function {a:?}\n{b}"),
+            Error::NotARecord(a, b) => write!(f, "Not a record {a:?}\n{b}"),
+            Error::NotAReference(a, b) => write!(f, "Not a reference {a:?}\n{b}"),
+            Error::NotABoolean(a, b) => write!(f, "Not a boolean {a:?}\n{b}"),
+            Error::ArgumentsMismatch(a) => write!(f, "Arguments mismatch\n{a}"),
+        }
+    }
 }
 
 impl From<ast::Error> for Error {
     fn from(error: ast::Error) -> Error {
         match error {
-            ast::Error::LabelNotFound(l) => Error::FieldNotFound(l),
+            ast::Error::LabelNotFound(l) => Error::FieldNotFound(l, Backtrace::capture()),
         }
     }
 }
@@ -57,6 +91,26 @@ pub struct State {
     env_namer: Namer,
     pub envs: Envs,
     pub variables: Variables,
+    pub primitive_funcs: PrimitiveFuncs,
+}
+
+pub struct PrimitiveFuncs {
+    pub map: HashMap<ast::Name, PrimFunc>,
+}
+
+pub type PrimFunc = fn(Vec<ast::Value>) -> ast::Value;
+
+impl PrimitiveFuncs {
+    pub fn new(prims: Vec<(&str, PrimFunc)>) -> Self {
+        let mut map: HashMap<ast::Name, PrimFunc> = HashMap::new();
+        for (key, func) in prims.into_iter() {
+            map.insert(key.into(), func);
+        }
+        PrimitiveFuncs { map }
+    }
+    pub fn get(&self, name: &ast::Name) -> Option<&PrimFunc> {
+        self.map.get(name)
+    }
 }
 
 pub struct Variables {
@@ -84,12 +138,13 @@ impl Variables {
     }
 }
 impl State {
-    pub fn new(name: String) -> State {
+    pub fn new(name: String, primitive_funcs: PrimitiveFuncs) -> State {
         State {
             name,
             env_namer: Namer::new(),
             envs: Envs(BTreeMap::new()),
             variables: Variables::new(),
+            primitive_funcs,
         }
     }
     pub fn generate_env(&mut self, env: Env) -> Result<ast::EnvName, Error> {
@@ -113,14 +168,16 @@ impl Env {
         }
     }
     pub fn get(&self, name: &ast::Name) -> Result<&ast::Value, Error> {
-        self.env.get(name).ok_or(Error::NameNotFound(name.clone()))
+        self.env
+            .get(name)
+            .ok_or(Error::NameNotFound(name.clone(), Backtrace::capture()))
     }
     pub fn insert(&mut self, name: ast::Name, value: ast::Value) {
         self.env.insert(name.clone(), value);
     }
     pub fn insert_nodup(&mut self, name: &ast::Name, value: ast::Value) -> Result<(), Error> {
         if self.env.insert(name.clone(), value).is_some() {
-            Err(Error::DuplicateNames(name.clone()))
+            Err(Error::DuplicateNames(name.clone(), Backtrace::capture()))
         } else {
             Ok(())
         }
@@ -134,16 +191,16 @@ impl Envs {
     pub fn get(&self, env_name: &ast::EnvName) -> Result<&Env, Error> {
         self.0
             .get(env_name)
-            .ok_or(Error::EnvNotFound(env_name.clone()))
+            .ok_or(Error::EnvNotFound(env_name.clone(), Backtrace::capture()))
     }
     pub fn get_mut(&mut self, env_name: &ast::EnvName) -> Result<&mut Env, Error> {
         self.0
             .get_mut(env_name)
-            .ok_or(Error::EnvNotFound(env_name.clone()))
+            .ok_or(Error::EnvNotFound(env_name.clone(), Backtrace::capture()))
     }
     pub fn insert(&mut self, name: &ast::EnvName, env: Env) -> Result<(), Error> {
         if self.0.insert(name.clone(), env).is_some() {
-            Err(Error::DuplicateEnvNames(name.clone()))
+            Err(Error::DuplicateEnvNames(name.clone(), Backtrace::capture()))
         } else {
             Ok(())
         }
diff --git a/src/main.rs b/src/main.rs
index 6965ef0..71ed8dc 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -29,7 +29,7 @@ async fn main() {
                 loop {
                     let events = fetch_events(&mut state);
                     update(&mut state, events);
-                    draw(&state);
+                    draw(&mut state);
                     next_frame().await;
                 }
             }
diff --git a/src/runtime/mod.rs b/src/runtime/mod.rs
index 16df112..b784f7d 100644
--- a/src/runtime/mod.rs
+++ b/src/runtime/mod.rs
@@ -1,3 +1,5 @@
+pub mod primitive_functions;
+
 pub mod runtime;
 pub use runtime::*;
 
diff --git a/src/runtime/primitive_functions.rs b/src/runtime/primitive_functions.rs
new file mode 100644
index 0000000..d346537
--- /dev/null
+++ b/src/runtime/primitive_functions.rs
@@ -0,0 +1,22 @@
+use crate::ast;
+use crate::interpret::PrimitiveFuncs;
+use macroquad::prelude::*;
+
+pub fn primitive_funcs() -> PrimitiveFuncs {
+    PrimitiveFuncs::new(vec![("frame_clear", clear)])
+}
+
+fn clear(args: Vec<ast::Value>) -> ast::Value {
+    let r = to_u32(args.get(0));
+    let g = to_u32(args.get(1));
+    let b = to_u32(args.get(2));
+    clear_background(Color::from_rgba(r, g, b, 255));
+    ast::UNIT_VALUE
+}
+
+fn to_u32(value: Option<&ast::Value>) -> u8 {
+    match value {
+        Some(ast::Value::Int(i)) => *i as u8,
+        _ => 0,
+    }
+}
diff --git a/src/runtime/runtime.rs b/src/runtime/runtime.rs
index 5ce600f..8369249 100644
--- a/src/runtime/runtime.rs
+++ b/src/runtime/runtime.rs
@@ -1,3 +1,4 @@
+use super::primitive_functions::primitive_funcs;
 use super::types::*;
 use crate::ast;
 use crate::ast::helpers;
@@ -8,11 +9,11 @@ use macroquad::prelude::*;
 pub async fn setup(code: ast::Program) -> State {
     let font = load_ttf_font("./assets/fonts/monogram.ttf").await.unwrap();
 
-    let mut state = match interpret::setup(code) {
+    let mut state = match interpret::setup(code, primitive_funcs()) {
         Ok(state) => state,
         Err(err) => {
             println!("Error: {}", err);
-            interpret::State::new("game".into())
+            interpret::State::new("game".into(), primitive_funcs())
         }
     };
     let game_state = match interpret::interpret(&mut state, "setup".into(), vec![]) {
@@ -32,7 +33,7 @@ pub async fn setup(code: ast::Program) -> State {
 }
 
 pub async fn migrate(mut state: State, code: ast::Program) -> State {
-    match interpret::setup(code) {
+    match interpret::setup(code, primitive_funcs()) {
         Err(err) => {
             println!("Error: {}", err);
             state
@@ -136,7 +137,7 @@ pub fn fetch_events(state: &mut State) -> Input {
     input
 }
 
-pub fn draw(state: &State) {
+pub fn draw(state: &mut State) {
     clear_background(Color::from_hex(0x081829));
 
     set_default_camera();
@@ -151,6 +152,15 @@ pub fn draw(state: &State) {
 
     set_default_camera();
 
+    match interpret::interpret(
+        &mut state.state,
+        "draw".into(),
+        vec![ast::Expr::Value(state.game_state.clone())],
+    ) {
+        Ok(_) => {}
+        Err(err) => println!("Error: {}", err),
+    }
+
     println!(
         "{:#?}",
         interpret::value_to_stadnalone_expr(&state.state, state.game_state.clone())