diff --git a/.gitignore b/.gitignore
index cfbed0e..7cf503f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,4 +7,7 @@ src/#*
 src/*~
 
 # history file
-.mal-history
\ No newline at end of file
+.mal-history
+
+# stupid macos
+.DS_Store
diff --git a/src/core.rs b/src/core.rs
index 9a5a871..8f24f0f 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -1,5 +1,4 @@
-use std::env;
-use std::rc::Rc;
+use std::{cell::RefCell, env, rc::Rc};
 
 use crate::env::{any_zero, arithmetic_op, car, comparison_op, env_new, env_set, mal_exit, Env};
 
@@ -36,7 +35,7 @@ use crate::parse_tools::read_file;
 use crate::printer::pr_str;
 use crate::reader::{read_str, Reader};
 use crate::types::MalType::{Atom, Fun, Int, List, Nil, Str};
-use crate::types::{mal_assert, mal_equals, MalErr};
+use crate::types::{mal_assert, mal_equals, reset_bang, MalErr};
 
 pub fn ns_init() -> Env {
     env_init!(None,
@@ -63,8 +62,9 @@ pub fn ns_init() -> Env {
         "assert"        => Fun(mal_assert, "Return an error if assertion fails"),
         "read-string"   => Fun(|a| read_str(Reader::new().push(car(a)?.if_string()?)).map_err(MalErr::severe), "Tokenize and read the first argument"),
         "slurp"         => Fun(|a| Ok(Str(read_file(car(a)?.if_string()?)?)), "Read a file and return the content as a string"),
-        "atom"          => Fun(|a| Ok(Atom(Rc::new(car(a)?.clone()))), "Return an atom pointing to the given arg"),
-        "deref"         => Fun(|a| Ok(car(a)?.if_atom()?.clone()), "Return the content of the atom argumet"),
+        "atom"          => Fun(|a| Ok(Atom(Rc::new(RefCell::new(car(a)?.clone())))), "Return an atom pointing to the given arg"),
+        "deref"         => Fun(|a| match car(a)? { Atom(a) => Ok(a.borrow().clone()), _ => todo!("Cacca suprema") }, "Return the content of the atom argumet"),
+        "reset!"        => Fun(reset_bang, "Set the value of the first argument to the second argument"),
         "env"           => Fun(|a| match env::var(car(a)?.if_string()?) {
             Ok(s) => Ok(Str(s.into())),
             _ => Ok(Nil),
diff --git a/src/printer.rs b/src/printer.rs
index 459c128..c2a3d40 100644
--- a/src/printer.rs
+++ b/src/printer.rs
@@ -53,7 +53,7 @@ pub fn pr_str(ast: &MalType, print_readably: bool) -> String {
         ),
         M::Fun(..) => "#<builtin>".to_string(),
         M::MalFun { .. } => "#<function>".to_string(),
-        M::Atom(sub) => format!("Atom({})", pr_str(sub, print_readably)),
+        M::Atom(sub) => format!("Atom({})", pr_str(&sub.borrow(), print_readably)),
     }
 }
 
diff --git a/src/reader.rs b/src/reader.rs
index 6b77eaf..c19bfd7 100644
--- a/src/reader.rs
+++ b/src/reader.rs
@@ -133,6 +133,13 @@ impl Reader {
                     self.read_form()?,
                 ])))
             }
+            "@" => {
+                self.next()?;
+                Ok(List(Rc::new([
+                    MalType::Sym("deref".into()),
+                    self.read_form()?,
+                ])))
+            }
             _ => self.read_atom(),
         }
     }
diff --git a/src/types.rs b/src/types.rs
index f93952e..c05be7a 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -1,5 +1,5 @@
 use crate::env::{car_cdr, Env};
-use std::{collections::HashMap, rc::Rc};
+use std::{cell::RefCell, collections::HashMap, rc::Rc};
 
 pub type MalStr = Rc<str>;
 pub type MalArgs = Rc<[MalType]>;
@@ -25,7 +25,7 @@ pub enum MalType {
     Str(MalStr),
     Int(isize),
     Bool(bool),
-    Atom(Rc<MalType>),
+    Atom(Rc<RefCell<MalType>>),
     Nil,
 }
 
@@ -75,29 +75,21 @@ impl MalType {
         }
     }
 
-    pub fn if_atom(&self) -> Result<&MalType, MalErr> {
-        match self {
-            Self::Atom(sym) => Ok(sym),
-            _ => Err(MalErr::unrecoverable(
-                format!("{:?} is not an atom", prt(self)).as_str(),
-            )),
-        }
-    }
-
     pub fn label_type(&self) -> MalType {
-        Key(match self {
-            M::Nil => "ʞ:nil",
-            M::Bool(_) => "ʞ:bool",
-            M::Int(_) => "ʞ:int",
-            M::Fun(_, _) | M::MalFun { .. } => "ʞ:lambda",
-            M::Key(_) => "ʞ:key",
-            M::Str(_) => "ʞ:string",
-            M::Sym(_) => "ʞ:symbol",
-            M::List(_) => "ʞ:list",
-            M::Vector(_) => "ʞ:vector",
-            M::Map(_) => "ʞ:map",
-            M::Atom(_) => "ʞ:atom",
-        }
+        Key(("ʞ:".to_owned()
+            + match self {
+                M::Nil => "nil",
+                M::Bool(_) => "bool",
+                M::Int(_) => "int",
+                M::Fun(_, _) | M::MalFun { .. } => "lambda",
+                M::Key(_) => "key",
+                M::Str(_) => "string",
+                M::Sym(_) => "symbol",
+                M::List(_) => "list",
+                M::Vector(_) => "vector",
+                M::Map(_) => "map",
+                M::Atom(_) => "atom",
+            })
         .into())
     }
 }
@@ -135,6 +127,22 @@ pub fn mal_assert(args: &[MalType]) -> MalRet {
     Ok(M::Nil)
 }
 
+pub fn reset_bang(args: &[MalType]) -> MalRet {
+    if args.len() < 2 {
+        return Err(MalErr::unrecoverable("reset requires two arguments"));
+    }
+    let val = &args[1];
+    match &args[0] {
+        M::Atom(sym) => {
+            *std::cell::RefCell::<_>::borrow_mut(sym) = val.clone();
+            Ok(val.clone())
+        }
+        _ => Err(MalErr::unrecoverable(
+            format!("{:?} is not an atom", prt(&args[1])).as_str(),
+        )),
+    }
+}
+
 #[derive(PartialEq, Clone, Copy, Debug)]
 pub enum Severity {
     Recoverable,