diff --git a/src/codegen.rs b/src/codegen.rs
index f7140ea..95c8a3d 100644
--- a/src/codegen.rs
+++ b/src/codegen.rs
@@ -1,13 +1,10 @@
-use std::{collections::HashMap, error::Error, fmt::Write};
+use std::{collections::HashMap, error::Error};
 
-use crate::{
-    parser::{Expr, Stmt},
-    tokenizer::{MotError, TokenType, error},
-};
+use crate::parser::{Expr, Stmt};
 
 pub struct Var {
-    var_type: String,
-    stack_offset: usize,
+    pub var_type: String,
+    pub stack_offset: usize,
 }
 
 pub struct Env {
@@ -19,9 +16,10 @@ impl Env {
     pub fn new() -> Env {
         Env {
             scopes: vec![HashMap::new()],
-            next_offset: 8,
+            next_offset: 1,
         }
     }
+
     pub fn push_scope(&mut self) {
         self.scopes.push(HashMap::new());
     }
@@ -32,7 +30,7 @@ impl Env {
 
     pub fn define_var(&mut self, name: String, var_type: String) -> usize {
         let offset = self.next_offset;
-        self.next_offset += 8;
+        self.next_offset += 1;
         self.scopes.last_mut().unwrap().insert(name, Var {
             var_type,
             stack_offset: offset,
@@ -50,250 +48,10 @@ impl Env {
     }
 }
 
-pub struct Codegen {
-    output: String,
-    label_counter: usize,
-}
-
-impl Codegen {
-    pub fn new() -> Codegen {
-        Codegen {
-            output: String::new(),
-            label_counter: 0,
-        }
-    }
-
-    pub fn emit_prologue(&mut self) -> Result<(), Box<dyn Error>> {
-        writeln!(
-            &mut self.output,
-            "section .data
-format db \"%ld\", 10, 0
-
-section .text
-extern printf
-
-print:
-    push rbp
-    mov rbp, rsp
-    mov rdi, format
-    mov rsi, rax
-    xor rax, rax
-    call printf
-    pop rbp
-    ret
-"
-        )?;
-        Ok(())
-    }
-
-    pub fn emit_epilogue(&mut self) -> Result<(), Box<dyn Error>> {
-        writeln!(&mut self.output, "section .note.GNU-stack")?;
-        writeln!(&mut self.output, "    db 0")?;
-        Ok(())
-    }
-
-    pub fn get_output(self) -> String {
-        self.output
-    }
-
-    pub fn label(&mut self) -> String {
-        self.label_counter += 1;
-        format!(".L{}", self.label_counter)
-    }
-
-    pub fn compile_stmt(&mut self, env: &mut Env, stmt: Stmt) -> Result<(), Box<dyn Error>> {
-        match stmt {
-            Stmt::Expression(expr) => self.compile_expr(env, expr)?,
-            Stmt::Var {
-                name,
-                var_type,
-                initializer,
-            } => {
-                // TODO: types
-                assert!(var_type.lexeme == "I64");
-
-                self.compile_expr(env, initializer)?;
-                let offset = env.define_var(name.lexeme.clone(), var_type.lexeme);
-                writeln!(&mut self.output, "    mov QWORD [rbp-{}], rax", offset)?;
-            }
-            Stmt::Block(statements) => {
-                env.push_scope();
-                for stmt in statements {
-                    self.compile_stmt(env, stmt)?;
-                }
-                env.pop_scope();
-            }
-            Stmt::If {
-                condition,
-                then_branch,
-                else_branch,
-            } => {
-                let else_label = self.label();
-                let end_label = self.label();
-
-                self.compile_expr(env, condition)?;
-                writeln!(&mut self.output, "    test rax, rax")?;
-                writeln!(&mut self.output, "    je {}", else_label)?;
-                self.compile_stmt(env, *then_branch.clone())?;
-                writeln!(&mut self.output, "    jmp {}", end_label)?;
-                writeln!(&mut self.output, "{}:", else_label)?;
-                self.compile_stmt(env, *else_branch.clone())?;
-                writeln!(&mut self.output, "{}:", end_label)?;
-            }
-            Stmt::While { condition, body } => {
-                let begin_label = self.label();
-                let end_label = self.label();
-
-                writeln!(&mut self.output, "{}:", begin_label)?;
-                self.compile_expr(env, condition)?;
-                writeln!(&mut self.output, "    test rax, rax")?;
-                writeln!(&mut self.output, "    je {}", end_label)?;
-                self.compile_stmt(env, *body.clone())?;
-                writeln!(&mut self.output, "    jmp {}", begin_label)?;
-                writeln!(&mut self.output, "{}:", end_label)?;
-            }
-            Stmt::Function { name, params, body } => {
-                assert!(params.is_empty()); // TODO
-
-                writeln!(&mut self.output, "global {}", name.lexeme)?;
-                writeln!(&mut self.output, "{}:", name.lexeme)?;
-                writeln!(&mut self.output, "    push rbp")?;
-                writeln!(&mut self.output, "    mov rbp, rsp")?;
-                writeln!(&mut self.output, "    sub rsp, 256")?; // TODO
-
-                self.compile_stmt(env, *body)?;
-
-                writeln!(&mut self.output, "    mov rsp, rbp")?;
-                writeln!(&mut self.output, "    pop rbp")?;
-                writeln!(&mut self.output, "    mov rax, 0")?;
-                writeln!(&mut self.output, "    ret")?;
-            }
-        }
-        Ok(())
-    }
-
-    pub fn compile_expr(&mut self, env: &mut Env, expr: Expr) -> Result<(), Box<dyn Error>> {
-        match expr {
-            Expr::Binary { left, op, right } => {
-                self.compile_expr(env, *left)?;
-                writeln!(&mut self.output, "    push rax")?;
-                self.compile_expr(env, *right)?;
-                writeln!(&mut self.output, "    mov rbx, rax")?;
-                writeln!(&mut self.output, "    pop rax")?;
-
-                match op.token_type {
-                    TokenType::Plus => writeln!(&mut self.output, "    add rax, rbx")?,
-                    TokenType::Minus => writeln!(&mut self.output, "    sub rax, rbx")?,
-                    TokenType::Star => writeln!(&mut self.output, "    imul rax, rbx")?,
-                    TokenType::Slash => {
-                        writeln!(&mut self.output, "    cqo")?;
-                        writeln!(&mut self.output, "    idiv rbx")?;
-                    }
-                    TokenType::Mod => {
-                        writeln!(&mut self.output, "    cqo")?;
-                        writeln!(&mut self.output, "    idiv rbx")?;
-                        writeln!(&mut self.output, "    mov rax, rdx")?;
-                    }
-                    TokenType::Xor => writeln!(&mut self.output, "    xor rax, rbx")?,
-                    TokenType::And => todo!(),
-                    TokenType::Or => todo!(),
-                    TokenType::DoubleEqual => {
-                        writeln!(&mut self.output, "    cmp rax, rbx")?;
-                        writeln!(&mut self.output, "    sete al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    TokenType::NotEqual => {
-                        writeln!(&mut self.output, "    cmp rax, rbx")?;
-                        writeln!(&mut self.output, "    setne al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    TokenType::Greater => {
-                        writeln!(&mut self.output, "    cmp rax, rbx")?;
-                        writeln!(&mut self.output, "    setg al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    TokenType::GreaterEqual => {
-                        writeln!(&mut self.output, "    cmp rax, rbx")?;
-                        writeln!(&mut self.output, "    setge al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    TokenType::Less => {
-                        writeln!(&mut self.output, "    cmp rax, rbx")?;
-                        writeln!(&mut self.output, "    setl al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    TokenType::LessEqual => {
-                        writeln!(&mut self.output, "    cmp rax, rbx")?;
-                        writeln!(&mut self.output, "    setle al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    _ => unreachable!(),
-                }
-            }
-            Expr::Grouping(expr) => self.compile_expr(env, *expr)?,
-            Expr::Literal(token) => match token.token_type {
-                TokenType::Number => writeln!(&mut self.output, "    mov rax, {}", token.lexeme)?,
-                TokenType::String => todo!(),
-                _ => unreachable!(),
-            },
-            Expr::Unary { op, right } => {
-                self.compile_expr(env, *right)?;
-                match op.token_type {
-                    TokenType::Minus => writeln!(&mut self.output, "    neg rax")?,
-                    TokenType::Bang => {
-                        writeln!(&mut self.output, "    test rax, rax")?;
-                        writeln!(&mut self.output, "    sete al")?;
-                        writeln!(&mut self.output, "    movzx rax, al")?;
-                    }
-                    _ => unreachable!(),
-                }
-            }
-            Expr::Variable(name) => {
-                let var = match env.get_var(&name.lexeme) {
-                    Some(x) => x,
-                    None => {
-                        return error!(name.loc, format!("undefined variable: {}", &name.lexeme));
-                    }
-                };
-                writeln!(
-                    &mut self.output,
-                    "    mov rax, QWORD [rbp-{}]",
-                    var.stack_offset
-                )?
-            }
-            Expr::Assign { name, value } => {
-                self.compile_expr(env, *value)?;
-
-                let var = match env.get_var(&name.lexeme) {
-                    Some(x) => x,
-                    None => {
-                        return error!(name.loc, format!("undefined variable: {}", &name.lexeme));
-                    }
-                };
-                writeln!(
-                    &mut self.output,
-                    "    mov QWORD [rbp-{}], rax",
-                    var.stack_offset
-                )?;
-            }
-            Expr::Call {
-                callee,
-                paren: _,
-                args,
-            } => {
-                let callee = match *callee {
-                    Expr::Variable(name) => name.lexeme,
-                    _ => todo!(),
-                };
-
-                // TODO
-                assert!(args.len() == 1);
-
-                self.compile_expr(env, args.first().unwrap().clone())?;
-                writeln!(&mut self.output, "    mov rdi, rax")?;
-                writeln!(&mut self.output, "    call {}", callee)?;
-            }
-        }
-        Ok(())
-    }
+pub trait Codegen {
+    fn emit_prologue(&mut self) -> Result<(), Box<dyn Error>>;
+    fn emit_epilogue(&mut self) -> Result<(), Box<dyn Error>>;
+    fn get_output(&self) -> String;
+    fn compile_stmt(&mut self, env: &mut Env, stmt: Stmt) -> Result<(), Box<dyn Error>>;
+    fn compile_expr(&mut self, env: &mut Env, expr: Expr) -> Result<(), Box<dyn Error>>;
 }
diff --git a/src/codegen_x86_64.rs b/src/codegen_x86_64.rs
new file mode 100644
index 0000000..144b4e9
--- /dev/null
+++ b/src/codegen_x86_64.rs
@@ -0,0 +1,257 @@
+use std::{error::Error, fmt::Write};
+
+use crate::{
+    codegen::{Codegen, Env},
+    parser::{Expr, Stmt},
+    tokenizer::{MotError, TokenType, error},
+};
+
+pub struct CodegenX86_64 {
+    output: String,
+    label_counter: usize,
+}
+
+impl CodegenX86_64 {
+    pub fn new_boxed() -> Box<dyn Codegen> {
+        Box::new(CodegenX86_64 {
+            output: String::new(),
+            label_counter: 0,
+        })
+    }
+
+    fn label(&mut self) -> String {
+        self.label_counter += 1;
+        format!(".L{}", self.label_counter)
+    }
+}
+
+impl Codegen for CodegenX86_64 {
+    fn emit_prologue(&mut self) -> Result<(), Box<dyn Error>> {
+        writeln!(
+            &mut self.output,
+            "section .data
+format db \"%ld\", 10, 0
+
+section .text
+extern printf
+
+print:
+    push rbp
+    mov rbp, rsp
+    mov rdi, format
+    mov rsi, rax
+    xor rax, rax
+    call printf
+    pop rbp
+    ret
+"
+        )?;
+        Ok(())
+    }
+
+    fn emit_epilogue(&mut self) -> Result<(), Box<dyn Error>> {
+        writeln!(&mut self.output, "section .note.GNU-stack")?;
+        writeln!(&mut self.output, "    db 0")?;
+        Ok(())
+    }
+
+    fn get_output(&self) -> String {
+        self.output.clone()
+    }
+
+    fn compile_stmt(&mut self, env: &mut Env, stmt: Stmt) -> Result<(), Box<dyn Error>> {
+        match stmt {
+            Stmt::Expression(expr) => self.compile_expr(env, expr)?,
+            Stmt::Var {
+                name,
+                var_type,
+                initializer,
+            } => {
+                // TODO: types
+                assert!(var_type.lexeme == "I64");
+
+                self.compile_expr(env, initializer)?;
+                let offset = env.define_var(name.lexeme.clone(), var_type.lexeme);
+                writeln!(&mut self.output, "    mov QWORD [rbp-{}], rax", offset * 8)?;
+            }
+            Stmt::Block(statements) => {
+                env.push_scope();
+                for stmt in statements {
+                    self.compile_stmt(env, stmt)?;
+                }
+                env.pop_scope();
+            }
+            Stmt::If {
+                condition,
+                then_branch,
+                else_branch,
+            } => {
+                let else_label = self.label();
+                let end_label = self.label();
+
+                self.compile_expr(env, condition)?;
+                writeln!(&mut self.output, "    test rax, rax")?;
+                writeln!(&mut self.output, "    je {}", else_label)?;
+                self.compile_stmt(env, *then_branch.clone())?;
+                writeln!(&mut self.output, "    jmp {}", end_label)?;
+                writeln!(&mut self.output, "{}:", else_label)?;
+                self.compile_stmt(env, *else_branch.clone())?;
+                writeln!(&mut self.output, "{}:", end_label)?;
+            }
+            Stmt::While { condition, body } => {
+                let begin_label = self.label();
+                let end_label = self.label();
+
+                writeln!(&mut self.output, "{}:", begin_label)?;
+                self.compile_expr(env, condition)?;
+                writeln!(&mut self.output, "    test rax, rax")?;
+                writeln!(&mut self.output, "    je {}", end_label)?;
+                self.compile_stmt(env, *body.clone())?;
+                writeln!(&mut self.output, "    jmp {}", begin_label)?;
+                writeln!(&mut self.output, "{}:", end_label)?;
+            }
+            Stmt::Function { name, params, body } => {
+                assert!(params.is_empty()); // TODO
+
+                writeln!(&mut self.output, "global {}", name.lexeme)?;
+                writeln!(&mut self.output, "{}:", name.lexeme)?;
+                writeln!(&mut self.output, "    push rbp")?;
+                writeln!(&mut self.output, "    mov rbp, rsp")?;
+                writeln!(&mut self.output, "    sub rsp, 256")?; // TODO
+
+                self.compile_stmt(env, *body)?;
+
+                writeln!(&mut self.output, "    mov rsp, rbp")?;
+                writeln!(&mut self.output, "    pop rbp")?;
+                writeln!(&mut self.output, "    mov rax, 0")?;
+                writeln!(&mut self.output, "    ret")?;
+            }
+        }
+        Ok(())
+    }
+
+    fn compile_expr(&mut self, env: &mut Env, expr: Expr) -> Result<(), Box<dyn Error>> {
+        match expr {
+            Expr::Binary { left, op, right } => {
+                self.compile_expr(env, *left)?;
+                writeln!(&mut self.output, "    push rax")?;
+                self.compile_expr(env, *right)?;
+                writeln!(&mut self.output, "    mov rbx, rax")?;
+                writeln!(&mut self.output, "    pop rax")?;
+
+                match op.token_type {
+                    TokenType::Plus => writeln!(&mut self.output, "    add rax, rbx")?,
+                    TokenType::Minus => writeln!(&mut self.output, "    sub rax, rbx")?,
+                    TokenType::Star => writeln!(&mut self.output, "    imul rax, rbx")?,
+                    TokenType::Slash => {
+                        writeln!(&mut self.output, "    cqo")?;
+                        writeln!(&mut self.output, "    idiv rbx")?;
+                    }
+                    TokenType::Mod => {
+                        writeln!(&mut self.output, "    cqo")?;
+                        writeln!(&mut self.output, "    idiv rbx")?;
+                        writeln!(&mut self.output, "    mov rax, rdx")?;
+                    }
+                    TokenType::Xor => writeln!(&mut self.output, "    xor rax, rbx")?,
+                    TokenType::And => todo!(),
+                    TokenType::Or => todo!(),
+                    TokenType::DoubleEqual => {
+                        writeln!(&mut self.output, "    cmp rax, rbx")?;
+                        writeln!(&mut self.output, "    sete al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    TokenType::NotEqual => {
+                        writeln!(&mut self.output, "    cmp rax, rbx")?;
+                        writeln!(&mut self.output, "    setne al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    TokenType::Greater => {
+                        writeln!(&mut self.output, "    cmp rax, rbx")?;
+                        writeln!(&mut self.output, "    setg al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    TokenType::GreaterEqual => {
+                        writeln!(&mut self.output, "    cmp rax, rbx")?;
+                        writeln!(&mut self.output, "    setge al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    TokenType::Less => {
+                        writeln!(&mut self.output, "    cmp rax, rbx")?;
+                        writeln!(&mut self.output, "    setl al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    TokenType::LessEqual => {
+                        writeln!(&mut self.output, "    cmp rax, rbx")?;
+                        writeln!(&mut self.output, "    setle al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    _ => unreachable!(),
+                }
+            }
+            Expr::Grouping(expr) => self.compile_expr(env, *expr)?,
+            Expr::Literal(token) => match token.token_type {
+                TokenType::Number => writeln!(&mut self.output, "    mov rax, {}", token.lexeme)?,
+                TokenType::String => todo!(),
+                _ => unreachable!(),
+            },
+            Expr::Unary { op, right } => {
+                self.compile_expr(env, *right)?;
+                match op.token_type {
+                    TokenType::Minus => writeln!(&mut self.output, "    neg rax")?,
+                    TokenType::Bang => {
+                        writeln!(&mut self.output, "    test rax, rax")?;
+                        writeln!(&mut self.output, "    sete al")?;
+                        writeln!(&mut self.output, "    movzx rax, al")?;
+                    }
+                    _ => unreachable!(),
+                }
+            }
+            Expr::Variable(name) => {
+                let var = match env.get_var(&name.lexeme) {
+                    Some(x) => x,
+                    None => {
+                        return error!(name.loc, format!("undefined variable: {}", &name.lexeme));
+                    }
+                };
+                writeln!(
+                    &mut self.output,
+                    "    mov rax, QWORD [rbp-{}]",
+                    var.stack_offset * 8
+                )?
+            }
+            Expr::Assign { name, value } => {
+                self.compile_expr(env, *value)?;
+
+                let var = match env.get_var(&name.lexeme) {
+                    Some(x) => x,
+                    None => {
+                        return error!(name.loc, format!("undefined variable: {}", &name.lexeme));
+                    }
+                };
+                writeln!(
+                    &mut self.output,
+                    "    mov QWORD [rbp-{}], rax",
+                    var.stack_offset * 8
+                )?;
+            }
+            Expr::Call {
+                callee,
+                paren: _,
+                args,
+            } => {
+                let callee = match *callee {
+                    Expr::Variable(name) => name.lexeme,
+                    _ => todo!(),
+                };
+
+                // TODO
+                assert!(args.len() == 1);
+
+                self.compile_expr(env, args.first().unwrap().clone())?;
+                writeln!(&mut self.output, "    mov rdi, rax")?;
+                writeln!(&mut self.output, "    call {}", callee)?;
+            }
+        }
+        Ok(())
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index a744621..76314fb 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,5 @@
 mod codegen;
+mod codegen_x86_64;
 mod parser;
 mod tokenizer;
 
@@ -21,7 +22,7 @@ fn compile_file(path: String) -> Result<(), Box<dyn Error>> {
     let parser = parser::Parser::new(tokens);
     let statements = parser.parse()?;
 
-    let mut codegen = codegen::Codegen::new();
+    let mut codegen = codegen_x86_64::CodegenX86_64::new_boxed();
     codegen.emit_prologue()?;
 
     let mut env = codegen::Env::new();