diff --git a/src/ast/graph.rs b/src/ast/graph.rs
index 10b9a5b..4bbd664 100644
--- a/src/ast/graph.rs
+++ b/src/ast/graph.rs
@@ -235,6 +235,12 @@ impl AstGraphBuilder {
                 self.add_expr(node, rvalue);
                 node
             },
+            ExprValue::CompoundAssign { lvalue, rvalue, .. } => {
+                let node = self.child(parent, expr.value.to_string());
+                self.add_expr(node, lvalue);
+                self.add_expr(node, rvalue);
+                node
+            },
             ExprValue::UnaryOp { op: _, operand } => {
                 let node = self.child(parent, expr.value.to_string());
                 self.add_expr(node, operand);
diff --git a/src/ast/parser/expr.rs b/src/ast/parser/expr.rs
index 7b3aeec..2b46579 100644
--- a/src/ast/parser/expr.rs
+++ b/src/ast/parser/expr.rs
@@ -344,12 +344,28 @@ impl Parser {
     }
     fn parse_assign(&mut self) -> Result<Expr, ParseProcessError> {
         let lvalue = self.parse_logical_or()?;
-        if self.peek().value != TokenValue::Equal {
-            return Ok(lvalue);
-        }
+        let compound_op = match self.peek().value {
+            TokenValue::Equal => None,
+            TokenValue::PlusEqual => Some(BinaryOp::Add),
+            TokenValue::MinusEqual => Some(BinaryOp::Sub),
+            TokenValue::StarEqual => Some(BinaryOp::Mul),
+            TokenValue::SlashEqual => Some(BinaryOp::Div),
+            TokenValue::PercentEqual => Some(BinaryOp::Mod),
+            _ => return Ok(lvalue),
+        };
         self.advance(1);
         let rvalue = self.parse_assign()?;
         let span = Span::from_two(lvalue.span, rvalue.span);
+        if let Some(op) = compound_op {
+            return Ok(Expr {
+                value: ExprValue::CompoundAssign {
+                    lvalue: Box::new(lvalue),
+                    op,
+                    rvalue: Box::new(rvalue),
+                },
+                span,
+            });
+        }
         Ok(Expr {
             value: ExprValue::Assign {
                 lvalue: Box::new(lvalue),
diff --git a/src/ast/types.rs b/src/ast/types.rs
index 5cbf27f..33baf18 100644
--- a/src/ast/types.rs
+++ b/src/ast/types.rs
@@ -104,10 +104,12 @@ pub struct ReturnStmt {
     pub value: Option<Expr>,
     pub span: Span,
 }
+#[derive(Clone)]
 pub struct Expr {
     pub value: ExprValue,
     pub span: Span,
 }
+#[derive(Clone)]
 pub enum ExprValue {
     IntLit(i64),
     Var(String),
@@ -134,6 +136,11 @@ pub enum ExprValue {
         lvalue: Box<Expr>, 
         rvalue: Box<Expr>
     },
+    CompoundAssign {
+        lvalue: Box<Expr>,
+        op: BinaryOp,
+        rvalue: Box<Expr>,
+    },
 }
 #[derive(Clone, Copy)]
 pub enum BinaryOp {
@@ -310,6 +317,7 @@ impl fmt::Display for ExprValue {
             ExprValue::BinaryOp { op, .. } => write!(f, "BinaryOp({})", op),
             ExprValue::FuncCall(name, _) => write!(f, "FuncCall({})", name),
             ExprValue::Assign { .. } => write!(f, "Assign"),
+            ExprValue::CompoundAssign { op, .. } => write!(f, "CompoundAssign({})", op),
             ExprValue::UnaryOp { op, .. } => write!(f, "UnaryOp({})", op),
             ExprValue::IncDec { op, is_prefix, .. } => write!(f, "{}{}", if *is_prefix { "Prefix" } else { "Postfix" }, op),
         }
diff --git a/src/ir/generator.rs b/src/ir/generator.rs
index 59183e0..200d52f 100644
--- a/src/ir/generator.rs
+++ b/src/ir/generator.rs
@@ -417,9 +417,48 @@ impl<'a> Generator<'a> {
                 let (lvalue_instrs, target, is_addr) = self.generate_lvalue(*lvalue)?;
                 instrs.extend(lvalue_instrs);
                 if is_addr {
-                    instrs.push(IRInstr::Store(target.clone(), rvalue_var.unwrap()));
+                    instrs.push(IRInstr::Store(target.clone(), rvalue_var));
                 } else {
-                    instrs.push(IRInstr::Move(target.clone(), MoveRValue::Var(rvalue_var.unwrap())));
+                    instrs.push(IRInstr::Move(target.clone(), MoveRValue::Var(rvalue_var)));
+                }
+                let temp_var = self.var_manager.declare_temp(lvalue_ty);
+                if is_addr {
+                    instrs.push(IRInstr::Load(temp_var.clone(), target));
+                } else {
+                    instrs.push(IRInstr::Move(temp_var.clone(), MoveRValue::Var(target)));
+                }
+                (instrs, Some(temp_var))
+            },
+            HirExprValue::CompoundAssign { lvalue, op, rvalue } => {
+                let lvalue_ty: IRType = lvalue.ty.clone().into();
+                let (mut instrs, target, is_addr) = self.generate_lvalue(*lvalue)?;
+                let mut old_var = self.var_manager.declare_temp(lvalue_ty.clone());
+                if is_addr {
+                    instrs.push(IRInstr::Load(old_var.clone(), target.clone()));
+                } else {
+                    instrs.push(IRInstr::Move(old_var.clone(), MoveRValue::Var(target.clone())));
+                }
+
+                self.current_exit_label.push(None);
+                let (rvalue_instrs, rvalue_var) = self.generate_expr(*rvalue)?;
+                self.current_exit_label.pop();
+                instrs.extend(rvalue_instrs);
+                let mut rvalue_var = rvalue_var.unwrap();
+
+                let convert_to = IRType::get_elevate_result(&old_var.data_type, &rvalue_var.data_type).unwrap();
+                if convert_to != old_var.data_type {
+                    old_var = self.coerce_value(&mut instrs, old_var, &convert_to);
+                }
+                if convert_to != rvalue_var.data_type {
+                    rvalue_var = self.coerce_value(&mut instrs, rvalue_var, &convert_to);
+                }
+                let computed = self.var_manager.declare_temp(convert_to);
+                instrs.push(IRInstr::Binary(computed.clone(), old_var, op.into(), rvalue_var));
+                let stored = self.coerce_value(&mut instrs, computed, &lvalue_ty);
+                if is_addr {
+                    instrs.push(IRInstr::Store(target.clone(), stored));
+                } else {
+                    instrs.push(IRInstr::Move(target.clone(), MoveRValue::Var(stored)));
                 }
                 let temp_var = self.var_manager.declare_temp(lvalue_ty);
                 if is_addr {
diff --git a/src/lexer/types.rs b/src/lexer/types.rs
index 4cb66bc..abc7d02 100644
--- a/src/lexer/types.rs
+++ b/src/lexer/types.rs
@@ -18,6 +18,7 @@ pub enum TokenValue {
     
     Plus, Minus, Star, Slash, Percent,
     PlusPlus, MinusMinus,
+    PlusEqual, MinusEqual, StarEqual, SlashEqual, PercentEqual,
     Equal, DoubleEqual, Not, NotEqual, Less, LessEqual, Greater, GreaterEqual, And, Or,
 
     LParen, RParen,
@@ -56,6 +57,11 @@ impl std::fmt::Display for TokenValue {
             TokenValue::Minus => write!(f, "`-`"),
             TokenValue::PlusPlus => write!(f, "`++`"),
             TokenValue::MinusMinus => write!(f, "`--`"),
+            TokenValue::PlusEqual => write!(f, "`+=`"),
+            TokenValue::MinusEqual => write!(f, "`-=`"),
+            TokenValue::StarEqual => write!(f, "`*=`"),
+            TokenValue::SlashEqual => write!(f, "`/=`"),
+            TokenValue::PercentEqual => write!(f, "`%=`"),
             TokenValue::Star => write!(f, "`*`"),
             TokenValue::Slash => write!(f, "`/`"),
             TokenValue::Percent => write!(f, "`%`"),
@@ -98,6 +104,7 @@ pub enum TokenKind {
     TypeIdent,
     
     Plus, Minus, Star, Slash, Percent,
+    PlusEqual, MinusEqual, StarEqual, SlashEqual, PercentEqual,
     Equal, DoubleEqual, NotEqual, Less, LessEqual, Greater, GreaterEqual,
 
     LParen, RParen,
diff --git a/src/sema/analyzer.rs b/src/sema/analyzer.rs
index e6b39f7..fad5e52 100644
--- a/src/sema/analyzer.rs
+++ b/src/sema/analyzer.rs
@@ -1,4 +1,4 @@
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet};
 
 use crate::{
     ast::types::{
@@ -21,6 +21,7 @@ use crate::{
 pub struct Analyzer {
     symbols: SymbolTable,
     function_map: BTreeMap<String, FunctionId>,
+    builtin_functions: BTreeSet<FunctionId>,
     functions: Vec<FunctionSig>,
     current_func_return_type: Option<SemaType>,
     diagnostic: Diagnositics,
@@ -32,6 +33,7 @@ impl Analyzer {
         let mut analyzer = Self {
             symbols: SymbolTable::new(),
             function_map: BTreeMap::new(),
+            builtin_functions: BTreeSet::new(),
             functions: vec![],
             current_func_return_type: None,
             diagnostic: Diagnositics::new(),
@@ -75,6 +77,7 @@ impl Analyzer {
             parameter_types,
         };
         self.function_map.insert(name.to_string(), id);
+        self.builtin_functions.insert(id);
         self.functions.push(sig);
     }
 
@@ -156,7 +159,11 @@ impl Analyzer {
     }
 
     fn analyze_func_decl(&mut self, func_decl: FuncDeclStmt) -> Option<HirFuncDeclStmt> {
-        if self.function_map.contains_key(&func_decl.name) {
+        let is_static = func_decl.storage_class == Some(StorageClass::Static);
+        let existing_function = self.function_map.get(&func_decl.name).cloned();
+        let can_shadow_builtin = is_static
+            && existing_function.is_some_and(|function| self.builtin_functions.contains(&function));
+        if existing_function.is_some() && !can_shadow_builtin {
             self.add_error(SemaError::FunctionHasBeenDefined(func_decl.name.clone()), func_decl.name_span);
             return None;
         }
@@ -167,9 +174,14 @@ impl Analyzer {
             parameter_types.push(self.build_var_type(param.param_type.into(), &param.dimensions, true));
         }
         let return_type: SemaType = func_decl.return_type.into();
+        let ir_name = if is_static {
+            format!("__static_func_{}_{}", function_id.0, func_decl.name)
+        } else {
+            func_decl.name.clone()
+        };
         let sig = FunctionSig {
             id: function_id,
-            name: func_decl.name.clone(),
+            name: ir_name,
             return_type: return_type.clone(),
             parameter_types,
         };
@@ -208,24 +220,31 @@ impl Analyzer {
 
     fn eval_const_expr(expr: &Expr) -> Option<i32> {
         match &expr.value {
-            ExprValue::IntLit(value) => i32::try_from(*value).ok(),
+            ExprValue::IntLit(value) => Some(*value as i32),
             ExprValue::UnaryOp { op, operand } => {
                 let value = Self::eval_const_expr(operand)?;
                 match op {
                     crate::ast::types::UnaryOp::Add => Some(value),
-                    crate::ast::types::UnaryOp::Sub => value.checked_neg(),
+                    crate::ast::types::UnaryOp::Sub => Some(value.wrapping_neg()),
                     crate::ast::types::UnaryOp::Not => Some((value == 0) as i32),
                 }
             }
             ExprValue::BinaryOp { lhs, op, rhs } => {
                 let lhs = Self::eval_const_expr(lhs)?;
+                match op {
+                    BinaryOp::And if lhs == 0 => return Some(0),
+                    BinaryOp::Or if lhs != 0 => return Some(1),
+                    _ => {}
+                }
                 let rhs = Self::eval_const_expr(rhs)?;
                 match op {
-                    BinaryOp::Add => lhs.checked_add(rhs),
-                    BinaryOp::Sub => lhs.checked_sub(rhs),
-                    BinaryOp::Mul => lhs.checked_mul(rhs),
-                    BinaryOp::Div => lhs.checked_div(rhs),
-                    BinaryOp::Mod => lhs.checked_rem(rhs),
+                    BinaryOp::Add => Some(lhs.wrapping_add(rhs)),
+                    BinaryOp::Sub => Some(lhs.wrapping_sub(rhs)),
+                    BinaryOp::Mul => Some(lhs.wrapping_mul(rhs)),
+                    BinaryOp::Div if rhs != 0 => Some(lhs.wrapping_div(rhs)),
+                    BinaryOp::Div => None,
+                    BinaryOp::Mod if rhs != 0 => Some(lhs.wrapping_rem(rhs)),
+                    BinaryOp::Mod => None,
                     BinaryOp::Equal => Some((lhs == rhs) as i32),
                     BinaryOp::NotEqual => Some((lhs != rhs) as i32),
                     BinaryOp::Less => Some((lhs < rhs) as i32),
@@ -248,12 +267,12 @@ impl Analyzer {
         for (i, dimension) in dimensions.iter().enumerate() {
             match &dimension.value {
                 Some(expr) => {
-                    if let ExprValue::IntLit(value) = expr.value {
+                    if let Some(value) = Self::eval_const_expr(expr) {
                         if value > 0 {
                             dims.push(value as usize);
-                        } else {
-                            self.add_error(SemaError::InvalidArrayDimension, dimension.span);
+                            continue;
                         }
+                        self.add_error(SemaError::InvalidArrayDimension, dimension.span);
                     } else {
                         self.add_error(SemaError::InvalidArrayDimension, dimension.span);
                     }
@@ -440,6 +459,7 @@ impl Analyzer {
                 })
             }
             ExprValue::Assign { lvalue, rvalue } => self.analyze_assign_expr(*lvalue, *rvalue, span),
+            ExprValue::CompoundAssign { lvalue, op, rvalue } => self.analyze_compound_assign_expr(*lvalue, op, *rvalue, span),
             ExprValue::ArrayAccess { array, index } => self.analyze_array_access_expr(*array, *index, span),
             ExprValue::UnaryOp { op, operand } => {
                 let operand_span = operand.span;
@@ -450,6 +470,7 @@ impl Analyzer {
                 }
                 let ty = match op {
                     crate::ast::types::UnaryOp::Not => SemaType::I1,
+                    crate::ast::types::UnaryOp::Add | crate::ast::types::UnaryOp::Sub if operand.ty == SemaType::I1 => SemaType::I32,
                     _ => operand.ty.clone(),
                 };
                 Some(HirExpr {
@@ -517,6 +538,50 @@ impl Analyzer {
         })
     }
 
+    fn analyze_compound_assign_expr(&mut self, lvalue: Expr, op: BinaryOp, rvalue: Expr, span: Span) -> Option<HirExpr> {
+        if !matches!(lvalue.value, ExprValue::Var(_) | ExprValue::ArrayAccess { .. }) {
+            self.add_error(SemaError::InvalidAssignmentTarget, lvalue.span);
+            return None;
+        }
+        let lvalue_span = lvalue.span;
+        let lvalue = self.analyze_expr(lvalue)?;
+        if lvalue.ty.is_array_like() {
+            self.add_error(SemaError::InvalidAssignmentTarget, lvalue.span);
+            return None;
+        }
+        let rvalue_span = rvalue.span;
+        let rvalue = self.analyze_expr(rvalue)?;
+        if !lvalue.ty.is_scalar() {
+            self.add_error(SemaError::InvalidOperand(lvalue.ty.clone()), lvalue_span);
+            return None;
+        }
+        if !rvalue.ty.is_scalar() {
+            self.add_error(SemaError::InvalidOperand(rvalue.ty.clone()), rvalue_span);
+            return None;
+        }
+        let result_ty = match SemaType::get_elevate_result(&lvalue.ty, &rvalue.ty) {
+            Some(ty) => ty,
+            None => {
+                self.add_error(SemaError::IncompatiableOperand(lvalue.ty.clone(), rvalue.ty.clone()), lvalue_span);
+                self.add_error(SemaError::IncompatiableOperand(lvalue.ty.clone(), rvalue.ty.clone()), rvalue_span);
+                return None;
+            }
+        };
+        if !self.type_matches(&lvalue.ty, &result_ty) {
+            self.add_error(SemaError::TypeMismatch(lvalue.ty.clone(), result_ty), span);
+            return None;
+        }
+        Some(HirExpr {
+            ty: lvalue.ty.clone(),
+            value: HirExprValue::CompoundAssign {
+                lvalue: Box::new(lvalue),
+                op,
+                rvalue: Box::new(rvalue),
+            },
+            span,
+        })
+    }
+
     fn analyze_binary_expr(&mut self, lhs: Expr, op: BinaryOp, rhs: Expr, span: Span) -> Option<HirExpr> {
         let lhs_span = lhs.span;
         let rhs_span = rhs.span;
@@ -619,7 +684,7 @@ impl Analyzer {
         let ty = match array.ty.indexed_type() {
             Some(ty) => ty,
             None => {
-                self.add_error(SemaError::NotSubscriptable, span);
+                self.add_error(SemaError::NotSubscriptable(array.ty.clone()), span);
                 return None;
             }
         };
@@ -637,6 +702,9 @@ impl Analyzer {
         if expected == actual {
             return true;
         }
+        if matches!((expected, actual), (SemaType::I32, SemaType::I1)) {
+            return true;
+        }
         if let (SemaType::Array(expected_elem, expected_dims), SemaType::Array(actual_elem, actual_dims)) = (expected, actual) {
             return expected_elem == actual_elem
                 && expected_dims.len() == actual_dims.len()
diff --git a/src/sema/hir.rs b/src/sema/hir.rs
index 133fbbc..3ad6f3b 100644
--- a/src/sema/hir.rs
+++ b/src/sema/hir.rs
@@ -127,4 +127,9 @@ pub enum HirExprValue {
         lvalue: Box<HirExpr>,
         rvalue: Box<HirExpr>,
     },
+    CompoundAssign {
+        lvalue: Box<HirExpr>,
+        op: BinaryOp,
+        rvalue: Box<HirExpr>,
+    },
 }