diff --git a/src/util/expression/ast.rs b/src/util/expression/ast.rs
new file mode 100644
index 0000000..b8bb240
--- /dev/null
+++ b/src/util/expression/ast.rs
@@ -0,0 +1,22 @@
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum BinaryOp {
+    Add,
+    Subtract,
+    Multiply,
+    Divide,
+    Modulus,
+}
+
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum UnaryOp {
+    Negate,
+    Not,
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Node {
+    Float(f64),
+    Integer(i64),
+    BinaryExpr { left: Box<Node>, op: BinaryOp, right: Box<Node> },
+    UnaryExpr { op: UnaryOp, expr: Box<Node> },
+}
diff --git a/src/util/expression/lexer.rs b/src/util/expression/lexer.rs
new file mode 100644
index 0000000..761c3ab
--- /dev/null
+++ b/src/util/expression/lexer.rs
@@ -0,0 +1,266 @@
+use std::{
+    fmt::{Debug, Display, Formatter},
+    iter::Peekable,
+    str::Chars,
+};
+
+use super::token::{ArithmeticOp, SourceLocation, Token};
+
+pub(super) struct Cursor<'a> {
+    input: &'a str,
+    iter: Peekable<Chars<'a>>,
+    /// Character position in the input string
+    pos: usize,
+    location: SourceLocation,
+}
+
+impl<'a> Cursor<'a> {
+    pub fn new(input: &str) -> Cursor {
+        Cursor { input, iter: input.chars().peekable(), pos: 0, location: SourceLocation { line: 1, column: 0 } }
+    }
+
+    pub fn pos(&self) -> usize {
+        self.pos
+    }
+
+    fn inc_pos(&mut self) {
+        let c = self.iter.peek();
+        if c == Some(&'\n') {
+            self.location.line += 1;
+            self.location.column = 0;
+        } else {
+            self.location.column += 1;
+        }
+        self.pos += 1;
+    }
+
+    pub fn next(&mut self) -> Option<char> {
+        let c = self.iter.next()?;
+        self.inc_pos();
+        Some(c)
+    }
+
+    pub fn next_if(&mut self, func: impl FnOnce(&char) -> bool) -> Option<char> {
+        let c = self.iter.peek()?;
+        if func(c) {
+            self.next()
+        } else {
+            None
+        }
+    }
+
+    pub fn peek(&mut self) -> Option<char> {
+        self.iter.peek().copied()
+    }
+}
+
+pub(super) struct Tokenizer<'a> {
+    cursor: Cursor<'a>,
+    pub tokens: Vec<(Token, SourceLocation)>,
+}
+
+impl Tokenizer<'_> {
+    pub fn new(input: &str) -> Tokenizer {
+        Tokenizer { cursor: Cursor::new(input), tokens: Vec::new() }
+    }
+
+    pub fn scan(&mut self) -> LexResult {
+        while let Some(c) = self.cursor.peek() {
+            self.scan_item(c)?;
+        }
+
+        Ok(())
+    }
+
+    fn next(&mut self) -> LexResult<char> {
+        self.cursor.next().ok_or_else(|| LexError::UnexpectedEndOfInput)
+    }
+
+    fn next_if(&mut self, func: impl FnOnce(&char) -> bool) -> LexResult<char> {
+        self.cursor.next_if(func).ok_or_else(|| LexError::UnexpectedEndOfInput)
+    }
+
+    fn scan_item(&mut self, c: char) -> LexResult {
+        match c {
+            ' ' | '\t' | '\n' => {
+                self.cursor.next();
+                return Ok(());
+            }
+            '0'..='9' => self.number(),
+            '+' | '-' | '*' | '/' | '%' => self.operator(),
+            '(' | ')' => self.bracket(),
+            _ => return self.unexpected(c),
+        }
+    }
+
+    fn number(&mut self) -> LexResult {
+        let mut value = String::new();
+        let mut is_fractional = false;
+        let loc = self.cursor.location;
+
+        while let Ok(c) = self.next_if(|c| matches!(c, '0'..='9' | '.')) {
+            if c == '.' {
+                if is_fractional {
+                    return self.unexpected(c);
+                }
+                is_fractional = true;
+            }
+
+            value.push(c);
+        }
+
+        self.tokens.push((Token::Number { value, is_fractional }, loc));
+
+        Ok(())
+    }
+
+    fn operator(&mut self) -> LexResult {
+        let loc = self.cursor.location;
+        let c = self.next()?;
+        match c {
+            '+' => self.tokens.push((Token::ArithmeticOp(ArithmeticOp::Add), loc)),
+            '-' => self.tokens.push((Token::ArithmeticOp(ArithmeticOp::Subtract), loc)),
+            '*' => self.tokens.push((Token::ArithmeticOp(ArithmeticOp::Multiply), loc)),
+            '/' => self.tokens.push((Token::ArithmeticOp(ArithmeticOp::Divide), loc)),
+            '%' => self.tokens.push((Token::ArithmeticOp(ArithmeticOp::Modulus), loc)),
+            _ => return self.unexpected(c),
+        }
+        Ok(())
+    }
+
+    fn bracket(&mut self) -> LexResult {
+        let loc = self.cursor.location;
+        let c = self.next()?;
+        match c {
+            '(' => self.tokens.push((Token::LeftParen, loc)),
+            ')' => self.tokens.push((Token::RightParen, loc)),
+            _ => return self.unexpected(c),
+        }
+        Ok(())
+    }
+
+    fn unexpected(&self, c: char) -> LexResult {
+        let loc = self.cursor.location;
+        Err(LexError::UnexpectedChar { c, loc })
+    }
+}
+
+pub type LexResult<T = ()> = Result<T, LexError>;
+
+pub enum LexError {
+    UnexpectedChar { c: char, loc: SourceLocation },
+    UnexpectedEndOfInput,
+}
+
+impl Display for LexError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            LexError::UnexpectedChar { c, loc } => {
+                write!(f, "Unexpected character '{}' at {}", c, loc)
+            }
+            LexError::UnexpectedEndOfInput => write!(f, "Unexpected end of input"),
+        }
+    }
+}
+
+impl Debug for LexError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        Display::fmt(self, f)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn test_expression(input: &str, result: Vec<Token>) {
+        let mut tok = Tokenizer::new(input);
+        tok.scan().unwrap();
+        // println!("tokens: {:?}", tok.tokens);
+        let tokens = tok.tokens.into_iter().map(|(t, _)| t).collect::<Vec<_>>();
+        assert_eq!(tokens, result);
+    }
+
+    #[test]
+    fn test_number() {
+        test_expression("1", vec![Token::Number { value: "1".to_string(), is_fractional: false }]);
+        test_expression("1.0", vec![Token::Number { value: "1.0".to_string(), is_fractional: true }]);
+    }
+
+    #[test]
+    fn test_arithmetic_ops() {
+        test_expression(
+            "1 + 22 * 33 / 4444 + 55555",
+            vec![
+                Token::Number { value: "1".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::Number { value: "22".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Multiply),
+                Token::Number { value: "33".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Divide),
+                Token::Number { value: "4444".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::Number { value: "55555".to_string(), is_fractional: false },
+            ],
+        );
+
+        test_expression(
+            "1.0 + 2.0",
+            vec![
+                Token::Number { value: "1.0".to_string(), is_fractional: true },
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::Number { value: "2.0".to_string(), is_fractional: true },
+            ],
+        );
+        test_expression(
+            "2.0 - 3",
+            vec![
+                Token::Number { value: "2.0".to_string(), is_fractional: true },
+                Token::ArithmeticOp(ArithmeticOp::Subtract),
+                Token::Number { value: "3".to_string(), is_fractional: false },
+            ],
+        );
+    }
+
+    #[test]
+    fn test_brackets() {
+        test_expression(
+            "(1 + 2)",
+            vec![
+                Token::LeftParen,
+                Token::Number { value: "1".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::Number { value: "2".to_string(), is_fractional: false },
+                Token::RightParen,
+            ],
+        );
+        test_expression(
+            "2 * (3 + 4)",
+            vec![
+                Token::Number { value: "2".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Multiply),
+                Token::LeftParen,
+                Token::Number { value: "3".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::Number { value: "4".to_string(), is_fractional: false },
+                Token::RightParen,
+            ],
+        );
+        test_expression(
+            "1 + ((2 * 3) + 4)",
+            vec![
+                Token::Number { value: "1".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::LeftParen,
+                Token::LeftParen,
+                Token::Number { value: "2".to_string(), is_fractional: false },
+                Token::ArithmeticOp(ArithmeticOp::Multiply),
+                Token::Number { value: "3".to_string(), is_fractional: false },
+                Token::RightParen,
+                Token::ArithmeticOp(ArithmeticOp::Add),
+                Token::Number { value: "4".to_string(), is_fractional: false },
+                Token::RightParen,
+            ],
+        );
+    }
+}
diff --git a/src/util/expression/mod.rs b/src/util/expression/mod.rs
new file mode 100644
index 0000000..bf2ceae
--- /dev/null
+++ b/src/util/expression/mod.rs
@@ -0,0 +1,5 @@
+pub mod ast;
+pub mod lexer;
+pub mod parser;
+pub mod token;
+pub mod vm;
\ No newline at end of file
diff --git a/src/util/expression/parser.rs b/src/util/expression/parser.rs
new file mode 100644
index 0000000..69626ef
--- /dev/null
+++ b/src/util/expression/parser.rs
@@ -0,0 +1,206 @@
+use std::fmt::{Debug, Display};
+
+use super::{
+    ast::{BinaryOp, Node, UnaryOp},
+    token::{ArithmeticOp, SourceLocation, Token},
+};
+
+pub struct Parser {
+    ast: Vec<Node>,
+    tokens: Vec<(Token, SourceLocation)>,
+    pos: usize,
+}
+
+// -- the grammar --
+// expression -> term
+// term -> factor ( ('+' | '-') factor )*
+// factor -> unary ( ('*' | '/' | '%') unary )*
+// unary -> ('!' | '-') unary | primary
+// primary -> NUMBER | '(' expression ')'
+
+impl Parser {
+    pub fn new(tokens: Vec<(Token, SourceLocation)>) -> Parser {
+        Parser { tokens, pos: 0, ast: Vec::new() }
+    }
+
+    fn current(&self) -> ParseResult<&(Token, SourceLocation)> {
+        self.tokens.get(self.pos).ok_or_else(|| ParseError::UnexpectedEnd)
+    }
+
+    fn advance(&mut self) {
+        self.pos += 1;
+    }
+
+    fn is_end(&self) -> bool {
+        self.pos >= self.tokens.len()
+    }
+
+    fn expect(&self, token: Token) -> bool {
+        !self.is_end() && self.current().map(|(t, _)| t == &token).unwrap_or(false)
+    }
+
+    fn parse_expr(&mut self) -> ParseResult<Node> {
+        self.parse_term()
+    }
+
+    fn parse_term(&mut self) -> ParseResult<Node> {
+        let mut node = self.parse_factor()?;
+
+        while !self.is_end() {
+            let op = if let (Token::ArithmeticOp(op), _) = self.current()? {
+                match op {
+                    ArithmeticOp::Add => BinaryOp::Add,
+                    ArithmeticOp::Subtract => BinaryOp::Subtract,
+                    _ => break,
+                }
+            } else {
+                break;
+            };
+
+            self.advance();
+            let right = self.parse_factor()?;
+            node = Node::BinaryExpr { left: Box::new(node), op, right: Box::new(right) };
+        }
+
+        Ok(node)
+    }
+
+    fn parse_factor(&mut self) -> ParseResult<Node> {
+        let mut node = self.parse_unary()?;
+
+        while !self.is_end() {
+            let op = if let (Token::ArithmeticOp(op), _) = self.current()? {
+                match op {
+                    ArithmeticOp::Multiply => BinaryOp::Multiply,
+                    ArithmeticOp::Divide => BinaryOp::Divide,
+                    ArithmeticOp::Modulus => BinaryOp::Modulus,
+                    _ => break,
+                }
+            } else {
+                break;
+            };
+
+            self.advance();
+            let right = self.parse_unary()?;
+            node = Node::BinaryExpr { left: Box::new(node), op, right: Box::new(right) };
+        }
+
+        Ok(node)
+    }
+
+    fn parse_unary(&mut self) -> ParseResult<Node> {
+        let current = self.current()?;
+        if let (Token::ArithmeticOp(ArithmeticOp::Subtract), _) = current {
+            self.advance();
+            let expr = self.parse_unary()?;
+            Ok(Node::UnaryExpr { op: UnaryOp::Negate, expr: Box::new(expr) })
+        } else {
+            self.parse_primary()
+        }
+    }
+
+    fn parse_primary(&mut self) -> ParseResult<Node> {
+        if let (Token::Number { .. }, _) = self.current()? {
+            let (current, loc) = self.current()?;
+            let node = match current {
+                Token::Number { value, is_fractional } => {
+                    if *is_fractional {
+                        Node::Float(value.parse().unwrap())
+                    } else {
+                        Node::Integer(value.parse().unwrap())
+                    }
+                }
+                _ => return Err(ParseError::UnexpectedToken { token: current.clone(), loc: *loc }),
+            };
+
+            self.advance();
+            Ok(node)
+        } else if self.expect(Token::LeftParen) {
+            self.advance();
+            let node = self.parse_expr()?;
+            if !self.expect(Token::RightParen) {
+                return self.unexpected();
+            }
+            self.advance();
+            Ok(node)
+        } else {
+            self.unexpected()
+        }
+    }
+
+    fn unexpected<T>(&self) -> ParseResult<T> {
+        let (token, loc) = self.current()?;
+        Err(ParseError::UnexpectedToken { token: token.clone(), loc: loc.clone() })
+    }
+
+    pub fn parse(&mut self) -> ParseResult {
+        let mut ast = Vec::new();
+        while !self.is_end() {
+            ast.push(self.parse_expr()?);
+        }
+
+        self.ast = ast;
+
+        Ok(())
+    }
+}
+
+type ParseResult<T = ()> = Result<T, ParseError>;
+
+pub enum ParseError {
+    UnexpectedToken { token: Token, loc: SourceLocation },
+    UnexpectedEnd,
+}
+
+impl Display for ParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ParseError::UnexpectedToken { token, loc } => {
+                write!(f, "Unexpected token {:?} at {}", token, loc)
+            }
+            ParseError::UnexpectedEnd => write!(f, "Unexpected end of input"),
+        }
+    }
+}
+
+impl Debug for ParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        Display::fmt(self, f)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::util::expression::{ast::BinaryOp, lexer::Tokenizer};
+
+    use super::*;
+
+    fn parse(input: &str) -> Vec<Node> {
+        let mut tokenizer = Tokenizer::new(input);
+        tokenizer.scan().unwrap();
+
+        let mut parser = Parser::new(tokenizer.tokens);
+        parser.parse().unwrap();
+
+        println!("{:#?}", parser.ast);
+        parser.ast
+    }
+
+    #[test]
+    fn test_parser() {
+        parse("-4 + (2 * 3) % 5 + (2 + 2) * 2");
+
+        assert_eq!(
+            parse("1 + 2 * 3"),
+            vec![Node::BinaryExpr {
+                left: Box::new(Node::Integer(1)),
+                op: BinaryOp::Add,
+                right: Box::new(Node::BinaryExpr {
+                    left: Box::new(Node::Integer(2)),
+                    op: BinaryOp::Multiply,
+                    right: Box::new(Node::Integer(3)),
+                }),
+            }]
+        );
+    }
+}
diff --git a/src/util/expression/token.rs b/src/util/expression/token.rs
new file mode 100644
index 0000000..3fc84c6
--- /dev/null
+++ b/src/util/expression/token.rs
@@ -0,0 +1,60 @@
+use std::fmt::Display;
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum ArithmeticOp {
+    Add,
+    Subtract,
+    Multiply,
+    Divide,
+    Modulus,
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum LogicalOp {
+    And,
+    Or,
+    Not,
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum ComparisonOp {
+    Equal,
+    NotEqual,
+    LessThan,
+    GreaterThan,
+    LessThanOrEqual,
+    GreaterThanOrEqual,
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum BitwiseOp {
+    And,
+    Or,
+    Xor,
+    Not,
+    ShiftLeft,
+    ShiftRight,
+}
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+pub enum Token {
+    Number { value: String, is_fractional: bool },
+    ArithmeticOp(ArithmeticOp),
+    LogicalOp(LogicalOp),
+    ComparisonOp(ComparisonOp),
+    BitwiseOp(BitwiseOp),
+    LeftParen,
+    RightParen,
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct SourceLocation {
+    pub line: usize,
+    pub column: usize,
+}
+
+impl Display for SourceLocation {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "line {}, column {}", self.line, self.column)
+    }
+}
diff --git a/src/util/expression/vm.rs b/src/util/expression/vm.rs
new file mode 100644
index 0000000..0af949e
--- /dev/null
+++ b/src/util/expression/vm.rs
@@ -0,0 +1,68 @@
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum VMOpcode {
+    // No operation
+    NOP,
+    // Pop the top value off the stack
+    STPOP,
+    // Loads a specified variable onto the stack
+    STLD(u16),
+    // Pushes a number onto the stack
+    STPSH(f64),
+    // Adds the top (int, int) from the stack
+    ADDII,
+    // Adds the top (float, float) from the stack
+    ADDFF,
+    // Subtracts the (int, int) from the stack
+    SUBII,
+    // Subtracts the (float, float) from the stack
+    SUBFF,
+    // Multiplies the top (int, int) from the stack
+    MULII,
+    // Multiplies the top (float, float) from the stack
+    MULFF,
+    // Divides the top (int, int) from the stack
+    DIVII,
+    // Divides the top (float, float) from the stack
+    DIVFF,
+    // Modulus of the top (int, int) from the stack
+    MODII,
+    // Modulus of the top (float, float) from the stack
+    MODFF,
+    // Calls a function with specified index and passes 1 argument from the stack
+    CALL1(u16),
+    // Calls a function with specified index and passes 2 arguments from the stack
+    CALL2(u16),
+    // Calls a function with specified index and passes 3 arguments from the stack
+    CALL3(u16),
+
+    // Intrinsics
+    // f64(int) -> f64
+    INFLOAT2INT,
+    // int(f64) -> int
+    ININT2FLOAT,
+    // frandom() -> f64
+    INFRAND,
+    // irandom() -> int
+    INIRAND,
+    // floor(f64) -> f64
+    INFLOOR,
+    // ceil(f64) -> f64
+    INCEIL,
+    // round(f64) -> f64
+    INROUND,
+    // abs(f64) -> f64
+    INABS,
+    // min(f64, f64) -> f64
+    INMIN,
+    // max(f64, f64) -> f64
+    INMAX,
+    // sqrt(f64) -> f64
+    INSQRT,
+    // cos(f64) -> f64
+    INCOS,
+    // sin(f64) -> f64
+    INSIN,
+}
+
+pub struct VM {
+}
\ No newline at end of file
diff --git a/src/util/mod.rs b/src/util/mod.rs
index 8cf1c5e..740717a 100644
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -1,4 +1,5 @@
 pub mod atom;
 pub mod bitvec;
 pub mod browser;
+pub mod expression;
 pub mod rng;