diff --git a/Cargo.lock b/Cargo.lock
index d08efc2..b134b8e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -77,6 +77,15 @@ checksum = "f8ca58f447f06ed17d5fc4043ce1b10dd205e060fb3ce5b979b8ed8e59ff3f79"
 [[package]]
 name = "mist"
 version = "0.1.0"
+dependencies = [
+ "parser",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "parser"
+version = "0.1.0"
 dependencies = [
  "pest",
  "pest_derive",
diff --git a/Cargo.toml b/Cargo.toml
index 3f1f1f9..9afc151 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,6 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-pest = "2.8.6"
-pest_derive = "2.8.6"
 serde = { version = "1.0.228", features = ["serde_derive"] }
 serde_json = "1.0.149"
+parser = { path = "./parser" }
diff --git a/parser/Cargo.toml b/parser/Cargo.toml
new file mode 100644
index 0000000..fcd7fd0
--- /dev/null
+++ b/parser/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "parser"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+pest = "2.8.6"
+pest_derive = "2.8.6"
+serde = { version = "1.0.228", features = ["serde_derive"] }
+serde_json = "1.0.149"
diff --git a/src/parser/ast.rs b/parser/src/ast.rs
similarity index 100%
rename from src/parser/ast.rs
rename to parser/src/ast.rs
diff --git a/src/parser/grammar.pest b/parser/src/grammar.pest
similarity index 100%
rename from src/parser/grammar.pest
rename to parser/src/grammar.pest
diff --git a/src/parser/mod.rs b/parser/src/lib.rs
similarity index 99%
rename from src/parser/mod.rs
rename to parser/src/lib.rs
index 152f95c..7b1a67a 100644
--- a/src/parser/mod.rs
+++ b/parser/src/lib.rs
@@ -5,7 +5,7 @@ pub mod ast;
 use ast::*;
 
 #[derive(Parser)]
-#[grammar = "./src/parser/grammar.pest"]
+#[grammar = "./src/grammar.pest"]
 pub struct MistParser;
 
 // convenience alias for pest errors
diff --git a/semantic/Cargo.toml b/semantic/Cargo.toml
new file mode 100644
index 0000000..c290a2c
--- /dev/null
+++ b/semantic/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "semantic"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/semantic/src/lib.rs b/semantic/src/lib.rs
new file mode 100644
index 0000000..b93cf3f
--- /dev/null
+++ b/semantic/src/lib.rs
@@ -0,0 +1,14 @@
+pub fn add(left: u64, right: u64) -> u64 {
+    left + right
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = add(2, 2);
+        assert_eq!(result, 4);
+    }
+}
diff --git a/src/compiler.rs b/src/compiler.rs
deleted file mode 100644
index 136aed5..0000000
--- a/src/compiler.rs
+++ /dev/null
@@ -1,96 +0,0 @@
-use std::{fs, path::PathBuf, process, time::Instant};
-
-use crate::{gogen, parser};
-
-use serde::Deserialize;
-
-#[derive(Deserialize)]
-struct Config {
-    entry: String,
-    out_dir: String,
-}
-
-pub fn build() {
-    let start = Instant::now();
-
-    // 1. find project root
-    let root = find_project_root().unwrap_or_else(|| {
-        panic!("error: could not find project root (mist.json)");
-    });
-
-    println!("mistc build ({})", root.display());
-
-    // 2. load config
-    let config = load_config(&root);
-
-    let entry_path = root.join(&config.entry);
-    let out_dir = root.join(&config.out_dir);
-
-    println!("  → entry: {}", entry_path.display());
-
-    // 3. read entry file
-    let source = match fs::read_to_string(&entry_path) {
-        Ok(s) => s,
-        Err(e) => {
-            eprintln!("error: failed to read entry file\n  {}", e);
-            process::exit(1);
-        }
-    };
-
-    println!("  → parsing...");
-
-    let ast = match parser::parse(&source) {
-        Ok(ast) => {
-            println!("  ✓ parsed {} items", ast.len());
-            ast
-        }
-        Err(e) => {
-            eprintln!("error: parse failed\n{}", e);
-            process::exit(1);
-        }
-    };
-
-    println!("  → generating Go code...");
-
-    // let output = gogen::generate(&ast);
-    let output = String::from("// TODO: implement code generation\n");
-
-    // 4. ensure build dir
-    if let Err(e) = fs::create_dir_all(&out_dir) {
-        eprintln!("error: failed to create build dir\n  {}", e);
-        process::exit(1);
-    }
-
-    let out_file = out_dir.join("main.go");
-
-    if let Err(e) = fs::write(&out_file, output) {
-        eprintln!("error: failed to write output\n  {}", e);
-        process::exit(1);
-    }
-
-    let elapsed = start.elapsed();
-
-    println!("  ✓ built {}", out_file.display());
-    println!("build finished in {:.2?}", elapsed);
-}
-
-pub fn find_project_root() -> Option<PathBuf> {
-    let mut dir = std::env::current_dir().ok()?;
-
-    loop {
-        if dir.join("mist.json").exists() {
-            return Some(dir);
-        }
-
-        if !dir.pop() {
-            return None;
-        }
-    }
-}
-
-fn load_config(root: &std::path::Path) -> Config {
-    let content =
-        std::fs::read_to_string(root.join("mist.json")).expect("failed to read mist.json");
-
-    serde_json::from_str(&content).expect("invalid mist.json format")
-}
diff --git a/src/errors.rs b/src/errors.rs
deleted file mode 100644
index e69de29..0000000
diff --git a/src/gogen/mod.rs b/src/gogen/mod.rs
deleted file mode 100644
index d41f710..0000000
--- a/src/gogen/mod.rs
+++ /dev/null
@@ -1,283 +0,0 @@
-// use crate::parser::ast::{
-//     BinOperator, Class, Expression, Function, Statement, Struct, TopLevel, TopLevel, TypeExpr,
-// };
-
-// pub fn generate(program: &TopLevel) -> String {
-//     let mut out = String::new();
-
-//     out.push_str("package main\n\n");
-
-//     // imports
-//     let mut imports = vec![];
-//     for item in &program.statements {
-//         if let TopLevel::Import(i) = item {
-//             imports.push(i.path.clone());
-//         }
-//     }
-
-//     if !imports.is_empty() {
-//         out.push_str("import (\n");
-//         for imp in imports {
-//             out.push_str(&format!("    {}\n", imp));
-//         }
-//         out.push_str(")\n\n");
-//     }
-
-//     // rest
-//     for item in &program.statements {
-//         match item {
-//             TopLevel::Function(f) => out.push_str(&gen_function(f)),
-//             TopLevel::Struct(s) => out.push_str(&gen_struct(s)),
-//             TopLevel::Class(c) => out.push_str(&gen_class(c)),
-//             TopLevel::Import(_) => {}
-//         }
-//         out.push('\n');
-//     }
-
-//     out
-// }
-
-// fn gen_struct(s: &Struct) -> String {
-//     let mut out = format!("type {} struct {{\n", s.name);
-
-//     for field in &s.fields {
-//         out.push_str(&format!(
-//             "    {} {}\n",
-//             capitalize(&field.name),
-//             gen_type(&field.type_expr)
-//         ));
-//     }
-
-//     out.push_str("}\n");
-//     out
-// }
-
-// fn gen_class(c: &Class) -> String {
-//     let mut out = String::new();
-
-//     // struct
-//     out.push_str(&format!("type {} struct {{\n", c.name));
-//     for field in &c.fields {
-//         out.push_str(&format!(
-//             "    {} {}\n",
-//             capitalize(&field.name),
-//             gen_type(&field.type_expr)
-//         ));
-//     }
-//     out.push_str("}\n\n");
-
-//     // methods
-//     for method in &c.methods {
-//         out.push_str(&gen_method(c, method));
-//         out.push('\n');
-//     }
-
-//     out
-// }
-
-// fn gen_function(f: &Function) -> String {
-//     let mut out = format!("func {}(", f.name);
-
-//     // params
-//     for (i, p) in f.params.iter().enumerate() {
-//         if i > 0 {
-//             out.push_str(", ");
-//         }
-//         out.push_str(&format!("{} {}", p.name, gen_type(&p.type_expr)));
-//     }
-
-//     out.push(')');
-
-//     // return
-//     if let Some(ret) = &f.return_type {
-//         out.push_str(&format!(" {}", gen_type(ret)));
-//     }
-
-//     out.push_str(" {\n");
-
-//     for stmt in &f.body {
-//         out.push_str(&gen_statement(stmt));
-//     }
-
-//     out.push_str("}\n");
-//     out
-// }
-
-// fn gen_method(class: &Class, f: &Function) -> String {
-//     let mut out = format!("func (self *{}) {}(", class.name, f.name);
-
-//     for (i, p) in f.params.iter().enumerate() {
-//         if i > 0 {
-//             out.push_str(", ");
-//         }
-//         out.push_str(&format!("{} {}", p.name, gen_type(&p.type_expr)));
-//     }
-
-//     out.push(')');
-
-//     if let Some(ret) = &f.return_type {
-//         out.push_str(&format!(" {}", gen_type(ret)));
-//     }
-
-//     out.push_str(" {\n");
-
-//     for stmt in &f.body {
-//         out.push_str(&gen_statement(stmt));
-//     }
-
-//     out.push_str("}\n");
-
-//     out
-// }
-
-// fn gen_statement(stmt: &Statement) -> String {
-//     match stmt {
-//         Statement::Let(s) => {
-//             let mut out = format!("    {} := {}", s.name, gen_expr(&s.value));
-
-//             out.push_str(";\n");
-//             out
-//         }
-
-//         Statement::Return(r) => match &r.value {
-//             Some(v) => format!("    return {};\n", gen_expr(v)),
-//             None => "    return;\n".to_string(),
-//         },
-
-//         Statement::Expression(e) => {
-//             format!("    {};\n", gen_expr(e))
-//         }
-
-//         Statement::If(i) => {
-//             let mut out = format!("    if {} {{\n", gen_expr(&i.condition));
-
-//             for stmt in &i.body {
-//                 out.push_str(&gen_statement(stmt));
-//             }
-
-//             out.push_str("    }");
-
-//             if let Some(else_body) = &i.else_body {
-//                 out.push_str(" else {\n");
-//                 for stmt in else_body {
-//                     out.push_str(&gen_statement(stmt));
-//                 }
-//                 out.push_str("    }");
-//             }
-
-//             out.push('\n');
-//             out
-//         }
-
-//         Statement::For(f) => {
-//             let mut out = format!(
-//                 "    for _, {} := range {} {{\n",
-//                 f.var,
-//                 gen_expr(&f.iterator)
-//             );
-
-//             for stmt in &f.body {
-//                 out.push_str(&gen_statement(stmt));
-//             }
-
-//             out.push_str("    }\n");
-//             out
-//         }
-//     }
-// }
-
-// fn gen_expr(expr: &Expression) -> String {
-//     match expr {
-//         Expression::Identifier(name, _) => name.clone(),
-//         Expression::Integer(v, _) => v.to_string(),
-//         Expression::Float(v, _) => v.to_string(),
-//         Expression::StringLit(s, _) => format!("\"{}\"", s),
-//         Expression::Bool(b, _) => b.to_string(),
-
-//         Expression::BinaryOp(b) => format!(
-//             "{} {} {}",
-//             gen_expr(&b.left),
-//             op_to_str(&b.op),
-//             gen_expr(&b.right)
-//         ),
-
-//         Expression::Call(c) => {
-//             let args = c.args.iter().map(gen_expr).collect::<Vec<_>>().join(", ");
-//             format!("{}({})", gen_expr(&c.callee), args)
-//         }
-
-//         Expression::FieldAccess(f) => {
-//             format!("{}.{}", gen_expr(&f.object), capitalize(&f.field))
-//         }
-
-//         Expression::StructInit(s) => {
-//             let mut out = format!("{}{{", s.name);
-
-//             for (i, (name, val)) in s.fields.iter().enumerate() {
-//                 if i > 0 {
-//                     out.push_str(", ");
-//                 }
-//                 out.push_str(&format!("{}: {}", capitalize(name), gen_expr(val)));
-//             }
-
-//             out.push('}');
-//             out
-//         }
-
-//         Expression::ArrayLiteral(arr) => {
-//             let elems = arr
-//                 .elements
-//                 .iter()
-//                 .map(gen_expr)
-//                 .collect::<Vec<_>>()
-//                 .join(", ");
-//             format!("[]any{{{}}}", elems) // simple version
-//         }
-
-//         _ => todo!(),
-//     }
-// }
-
-// fn gen_type(t: &TypeExpr) -> String {
-//     match t {
-//         TypeExpr::Named(n) => match n.as_str() {
-//             "int" => "int".into(),
-//             "float" => "float64".into(),
-//             "string" => "string".into(),
-//             _ => n.clone(),
-//         },
-
-//         TypeExpr::Array(inner) => {
-//             format!("[]{}", gen_type(inner))
-//         }
-
-//         TypeExpr::Optional(inner) => {
-//             format!("*{}", gen_type(inner)) // pointer for optional
-//         }
-//     }
-// }
-
-// fn capitalize(s: &str) -> String {
-//     let mut chars = s.chars();
-//     match chars.next() {
-//         Some(c) => c.to_uppercase().collect::<String>() + chars.as_str(),
-//         None => String::new(),
-//     }
-// }
-
-// fn op_to_str(op: &BinOperator) -> &'static str {
-//     match op {
-//         BinOperator::Add => "+",
-//         BinOperator::Sub => "-",
-//         BinOperator::Mul => "*",
-//         BinOperator::Div => "/",
-//         BinOperator::Eq => "==",
-//         BinOperator::NotEq => "!=",
-//         BinOperator::Lt => "<",
-//         BinOperator::Gt => ">",
-//         BinOperator::LtEq => "<=",
-//         BinOperator::GtEq => ">=",
-//         BinOperator::And => "&&",
-//         BinOperator::Or => "||",
-//     }
-// }
diff --git a/src/gogen/sourcemap.rs b/src/gogen/sourcemap.rs
deleted file mode 100644
index e69de29..0000000
diff --git a/src/main.rs b/src/main.rs
index d2d17ea..ad40e2b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,8 +1,3 @@
-pub mod compiler;
-pub mod errors;
-pub mod gogen;
-pub mod parser;
-
 use std::fs;
 use std::path::PathBuf;
 use std::process;
@@ -52,7 +47,7 @@ fn main() {
 }
 
 pub fn cmd_build() {
-    compiler::build();
+    unimplemented!("build command is not implemented yet");
 }
 
 fn cmd_check(path: &str) {