diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000..4b8c354
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,30 @@
+{
+    "$schema": "https://raw.githubusercontent.com/mfussenegger/dapconfig-schema/master/dapconfig-schema.json",
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "lldb",
+            "request": "launch",
+            "name": "Run Lox Interpreter",
+            "cargo": {
+                "args": [
+                    "build",
+                    "--package",
+                    "rox",
+                    "--message-format",
+                    "json"
+                ]
+            },
+            "program": "${workspaceFolder}/target/debug/rox",
+            "args": [
+                "run",
+                "-s",
+                "./lox/simple_for.lox"
+            ],
+            "env": {
+                "RUST_LOG": "debug"
+            },
+            "cwd": "${workspaceFolder}"
+        }
+    ]
+}
diff --git a/bf/fibonacci.bf b/bf/fibonacci.bf
new file mode 100644
index 0000000..ac429e9
--- /dev/null
+++ b/bf/fibonacci.bf
@@ -0,0 +1,6 @@
+>++++++++++>+>+[
+    [+++++[>++++++++<-]>.<++++++[>--------<-]+<<<]>.>>[
+        [-]<[>+<-]>>[<<+>+>-]<[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-
+            [>+<-[>+<-[>+<-[>[-]>+>+<<<-[>+<-]]]]]]]]]]]+>>>
+    ]<<<
+]
diff --git a/bf/helloworld.bf b/bf/helloworld.bf
new file mode 100644
index 0000000..8fa0f72
--- /dev/null
+++ b/bf/helloworld.bf
@@ -0,0 +1 @@
+++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.
diff --git a/bf/simple_loop.bf b/bf/simple_loop.bf
new file mode 100644
index 0000000..ffa6054
--- /dev/null
+++ b/bf/simple_loop.bf
@@ -0,0 +1 @@
+++++++[>++++++++<-]>. // prints '0'
diff --git a/lox/nested_while.lox b/lox/nested_while.lox
new file mode 100644
index 0000000..31a7e2a
--- /dev/null
+++ b/lox/nested_while.lox
@@ -0,0 +1,14 @@
+{
+  var i = 0;
+  var j = 0;
+  while (i < 10) {
+    print i;
+
+    while (j < 100) {
+      print j;
+      j = j + 1;
+    }
+ 
+    i = i + 1;
+  }
+}
diff --git a/lox/scope.lox b/lox/scope.lox
new file mode 100644
index 0000000..99293e7
--- /dev/null
+++ b/lox/scope.lox
@@ -0,0 +1,8 @@
+var a = "outer";
+
+{
+  var a = "inner";
+  print a; // expect: inner
+}
+
+print a;
diff --git a/lox/simple_for.lox b/lox/simple_for.lox
new file mode 100644
index 0000000..1c15ec5
--- /dev/null
+++ b/lox/simple_for.lox
@@ -0,0 +1,3 @@
+for (var i = 0; i < 10; i = i + 1) {
+  print i;
+}
diff --git a/lox/simple_while.lox b/lox/simple_while.lox
new file mode 100644
index 0000000..2acbf36
--- /dev/null
+++ b/lox/simple_while.lox
@@ -0,0 +1,5 @@
+var i = 0;
+while (i < 10) {
+  print i;
+  i = i + 1;
+}
diff --git a/src/environment.rs b/src/environment.rs
index edfd980..e8e4747 100644
--- a/src/environment.rs
+++ b/src/environment.rs
@@ -99,16 +99,14 @@ impl Environment {
 
     /// Find an environment at a specific lexical distance from the current one.
     fn ancestor(&self, distance: usize) -> Result<Environment, EnvironmentError> {
-        let mut environment = self.clone();
-
-        for _ in 0..distance {
-            let enclosing = match &environment.enclosing {
-                Some(enc) => enc.borrow().clone(),
-                None => return Err(EnvironmentError::InvalidDistance),
-            };
-            environment = enclosing;
+        // println!("{distance}: {self:?}");
+        if distance == 0 {
+            return Ok(self.clone());
         }
 
-        Ok(environment)
+        match &self.enclosing {
+            Some(enclosing) => enclosing.borrow().ancestor(distance - 1),
+            None => Err(EnvironmentError::InvalidDistance),
+        }
     }
 }
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 0388687..dabd215 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -52,9 +52,9 @@ pub struct Interpreter {
     /// Global environment containing built-in functions and top-level variables
     pub globals: Rc<RefCell<Environment>>,
     /// Current environment for variable lookups and assignments
-    environment: Rc<RefCell<Environment>>,
+    pub environment: Rc<RefCell<Environment>>,
     /// Map of expressions to their lexical distance for variable resolution
-    locals: HashMap<Expression, usize>,
+    pub locals: HashMap<Expression, usize>,
 }
 
 /// Default configuration for the interpreter, with builtin native functions.
@@ -452,11 +452,6 @@ impl Interpreter {
     fn assign(&mut self, name: &Token, expression: &Expression) -> Result<Value, InterpreterError> {
         let value = self.evaluate(expression)?;
 
-        self.environment
-            .borrow_mut()
-            .assign(name, value.clone())
-            .map_err(InterpreterError::UndefinedVariable)?;
-
         if let Some(distance) = self.locals.get(expression) {
             self.environment
                 .borrow_mut()
diff --git a/src/lib.rs b/src/lib.rs
index d27e546..c072493 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -94,6 +94,9 @@ fn run_rox(input: &str, interpreter: &mut Interpreter) -> Result<(), RoxError> {
     debug!("AST:\n{}", crate::ast_printer::print(&ast));
 
     resolver.resolve(&ast)?;
+    println!("globals: {:?}", interpreter.globals);
+    println!("environment: {:?}", interpreter.environment);
+    println!("locals: {:?}", interpreter.locals);
     interpreter.run(ast)?;
 
     Ok(())
diff --git a/src/native_functions.rs b/src/native_functions.rs
index c02c6ca..f72b221 100644
--- a/src/native_functions.rs
+++ b/src/native_functions.rs
@@ -3,7 +3,7 @@ use ordered_float::OrderedFloat;
 use std::{
     collections::HashMap,
     fs::File,
-    io::{BufReader, ErrorKind, Read},
+    io::{stdin, stdout, BufReader, ErrorKind, Read, Seek, SeekFrom, Write},
     rc::Rc,
     sync::RwLock,
     time::{SystemTime, UNIX_EPOCH},
@@ -53,7 +53,7 @@ impl Callable for ReadFile {
     }
 
     fn arity(&self) -> usize {
-        1
+        2
     }
 
     fn call(
@@ -61,18 +61,24 @@ impl Callable for ReadFile {
         _interpreter: &mut Interpreter,
         args: Vec<Value>,
     ) -> Result<Value, CallingError> {
-        if args.len() != self.arity() {
-            return Err(CallingError::ArgumentMismatch(self.arity(), args.len()));
-        }
-
-        let file_path = args
-            .first()
-            .ok_or(CallingError::CallFailed("arg not readable".into()))?;
+        let file_path = args.first().ok_or(CallingError::CallFailed(
+            "first arg must be file path".into(),
+        ))?;
         if let Value::String(file_path) = file_path {
             self.ensure_file_handle(file_path)?;
             let mut file_handles = FILE_HANDLES.write().unwrap();
             let reader = file_handles.get_mut(file_path).unwrap();
             let mut buffer = [0; 1];
+
+            let backwards = args.get(1).unwrap_or(&Value::Boolean(false));
+            if let Value::Boolean(backwards) = backwards {
+                if *backwards {
+                    reader
+                        .seek(SeekFrom::Current(-2))
+                        .map_err(|e| CallingError::CallFailed(e.to_string()))?;
+                }
+            }
+
             let character = match reader.read_exact(&mut buffer) {
                 Ok(_) => {
                     let character = buffer[0] as char;
@@ -143,9 +149,81 @@ impl Callable for Out {
     }
 }
 
+struct AsciiOut;
+impl Callable for AsciiOut {
+    fn name(&self) -> String {
+        "asciiOut".into()
+    }
+
+    fn arity(&self) -> usize {
+        1
+    }
+
+    fn call(&self, interpreter: &mut Interpreter, args: Vec<Value>) -> Result<Value, CallingError> {
+        if args.len() != self.arity() {
+            return Err(CallingError::ArgumentMismatch(self.arity(), args.len()));
+        }
+
+        let value = args
+            .first()
+            .ok_or(CallingError::CallFailed("arg not readable".into()))?;
+        if let Value::Number(value) = value {
+            let ascii = value.0 as u8 as char;
+            print!("{ascii}");
+
+            Ok(Value::Nil)
+        } else {
+            Err(CallingError::CallFailed(
+                "file_path arg must be a number".into(),
+            ))
+        }
+    }
+}
+
+struct PromptAscii;
+impl Callable for PromptAscii {
+    fn name(&self) -> String {
+        "prompt_ascii".into()
+    }
+
+    fn arity(&self) -> usize {
+        1
+    }
+
+    fn call(
+        &self,
+        _interpreter: &mut Interpreter,
+        args: Vec<Value>,
+    ) -> Result<Value, CallingError> {
+        if args.len() != self.arity() {
+            return Err(CallingError::ArgumentMismatch(self.arity(), args.len()));
+        }
+
+        let prompt = args
+            .first()
+            .ok_or(CallingError::CallFailed("arg not readable".into()))?;
+        if let Value::String(prompt) = prompt {
+            print!("{prompt} ");
+            stdout().flush();
+
+            let mut buffer = [0; 1];
+            stdin().read_exact(&mut buffer);
+
+            todo!()
+            // Ok(Value::Number(buffer[0] as char))
+        } else {
+            Err(CallingError::CallFailed("prompt must be a string".into()))
+        }
+    }
+}
+
 /// Return all native functions available to the Lox interpreter
 pub fn all() -> Vec<(String, Value)> {
     vec![
+        (
+            "asciiOut".into(),
+            Value::Callable((Rc::new(AsciiOut {}), CallableType::Function)),
+        ),
         (
             "clock".into(),
             Value::Callable((Rc::new(Clock {}), CallableType::Function)),
@@ -158,5 +236,9 @@ pub fn all() -> Vec<(String, Value)> {
             "read".into(),
             Value::Callable((Rc::new(ReadFile {}), CallableType::Function)),
         ),
+        (
+            "prompt".into(),
+            Value::Callable((Rc::new(PromptAscii {}), CallableType::Function)),
+        ),
     ]
 }
diff --git a/src/value.rs b/src/value.rs
index db858a5..cc1ff27 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -4,7 +4,7 @@ use ordered_float::OrderedFloat;
 
 use crate::{callable::Callable, instance, token::Literal};
 
-/// Represents the type of a callable value in Lox.
+/// Represent the type of a callable value in Lox.
 #[derive(Clone, Debug, PartialEq)]
 pub enum CallableType {
     /// A regular function or method