diff --git a/src/compiler/parser/mod.rs b/src/compiler/parser/mod.rs
index c030dd9..eb6abea 100644
--- a/src/compiler/parser/mod.rs
+++ b/src/compiler/parser/mod.rs
@@ -77,7 +77,7 @@ fn parse_expression<'source>(
         &["or"],                 // 1
         &["and"],                // 2
         &["==", "!="],           // 3
-        &["<", "<=", "=>", ">"], // 4
+        &["<", "<=", ">=", ">"], // 4
         &["+", "-"],             // 5
         &["*", "/", "%"],        // 6
         &["not", "-"],           // 7
diff --git a/src/compiler/symtab.rs b/src/compiler/symtab.rs
index dae6f66..a1cae10 100644
--- a/src/compiler/symtab.rs
+++ b/src/compiler/symtab.rs
@@ -51,7 +51,9 @@ impl<'source> SymTab<'source, Type> {
             (">", Func(vec![Int, Int], Box::new(Bool))),
             (">=", Func(vec![Int, Int], Box::new(Bool))),
             ("not", Func(vec![Bool], Box::new(Bool))),
-            ("neg", Func(vec![Bool], Box::new(Bool))),
+            ("neg", Func(vec![Int], Box::new(Int))),
+            ("or", Func(vec![Bool, Bool], Box::new(Bool))),
+            ("and", Func(vec![Bool, Bool], Box::new(Bool))),
         ]);
 
         SymTab {
diff --git a/src/compiler/type_checker.rs b/src/compiler/type_checker.rs
index d3ce620..6f78a95 100644
--- a/src/compiler/type_checker.rs
+++ b/src/compiler/type_checker.rs
@@ -9,14 +9,140 @@ pub fn type_check<'source>(ast: &Expression<'source>, symbols: &mut SymTab<'sour
         EmptyLiteral(_) => Type::Unit,
         IntLiteral(_, _) => Type::Int,
         BoolLiteral(_, _) => Type::Bool,
-        Identifier(_, _) => todo!(),
-        UnaryOp(_, _, _) => todo!(),
-        BinaryOp(_, _, _, _) => todo!(),
-        VarDeclaration(_, _, _) => Type::Unit,
-        Conditional(_, _, _, _) => todo!(),
-        While(_, _, _) => todo!(),
-        FunCall(_, _, _) => todo!(),
-        Block(_, _) => todo!(),
+        Identifier(_, name) => symbols.get(name).clone(),
+        UnaryOp(_, op, expr) => match *op {
+            "-" => {
+                let expr_types = vec![type_check(expr, symbols)];
+
+                let Type::Func(sig_arg_types, sig_ret_type) = symbols.get("neg") else {
+                    panic!("Identifier {} does not correspond to an operator!", op);
+                };
+
+                if expr_types != *sig_arg_types {
+                    panic!(
+                        "Operator {} argument types {:?} don't match expected {:?}",
+                        op, expr_types, *sig_arg_types
+                    );
+                }
+
+                (**sig_ret_type).clone()
+            }
+            _ => {
+                let expr_types = vec![type_check(expr, symbols)];
+
+                let Type::Func(sig_arg_types, sig_ret_type) = symbols.get(op) else {
+                    panic!("Identifier {} does not correspond to an operator!", op);
+                };
+
+                if expr_types != *sig_arg_types {
+                    panic!(
+                        "Operator {} argument types {:?} don't match expected {:?}",
+                        op, expr_types, *sig_arg_types
+                    );
+                }
+
+                (**sig_ret_type).clone()
+            }
+        },
+        BinaryOp(_, left, op, right) => match *op {
+            "==" | "!=" => {
+                let left_type = type_check(left, symbols);
+                let right_type = type_check(right, symbols);
+                if left_type != right_type {
+                    panic!("Mismatched types being compared with {op}");
+                }
+                Type::Bool
+            }
+            "=" => {
+                if !matches!(**left, Identifier(_, _)) {
+                    panic!("Non-variable on left side of assignment!");
+                }
+
+                let left_type = type_check(left, symbols);
+                let right_type = type_check(right, symbols);
+                if left_type != right_type {
+                    panic!("Mismatched types in assignment!");
+                }
+                left_type
+            }
+            _ => {
+                let left_type = type_check(left, symbols);
+                let right_type = type_check(right, symbols);
+                let arg_types = vec![left_type, right_type];
+
+                let Type::Func(sig_arg_types, sig_ret_type) = symbols.get(op) else {
+                    panic!("Identifier {} does not correspond to an operator!", op);
+                };
+
+                if arg_types != *sig_arg_types {
+                    panic!(
+                        "Operator {} argument types {:?} don't match expected {:?}",
+                        op, arg_types, *sig_arg_types
+                    );
+                }
+
+                (**sig_ret_type).clone()
+            }
+        },
+        VarDeclaration(_, name, expr) => {
+            let type_var = type_check(expr, symbols);
+            symbols.insert(name, type_var);
+            Type::Unit
+        }
+        Conditional(_, condition_expr, then_expr, else_expr) => {
+            if !matches!(type_check(condition_expr, symbols), Type::Bool) {
+                panic!("Non-bool as if-then-else condition!");
+            }
+
+            if let Some(else_expr) = else_expr {
+                let then_type = type_check(then_expr, symbols);
+                let else_type = type_check(else_expr, symbols);
+                if then_type == else_type {
+                    then_type
+                } else {
+                    panic!("Mismatched return values in if-then-else!");
+                }
+            } else {
+                Type::Unit
+            }
+        }
+        While(_, condition_expr, do_expr) => {
+            if !matches!(type_check(condition_expr, symbols), Type::Bool) {
+                panic!("Non-bool as while-do condition!");
+            }
+            type_check(do_expr, symbols);
+            Type::Unit
+        }
+        FunCall(_, name, args) => {
+            let mut arg_types = Vec::new();
+            for arg in args {
+                arg_types.push(type_check(arg, symbols));
+            }
+
+            let Type::Func(sig_arg_types, sig_ret_type) = symbols.get(name) else {
+                panic!("Identifier {} does not correspond to a function!", name);
+            };
+
+            if arg_types != *sig_arg_types {
+                panic!(
+                    "Function {} argument types {:?} don't match expected {:?}",
+                    name, arg_types, *sig_arg_types
+                );
+            }
+
+            (**sig_ret_type).clone()
+        }
+        Block(_, expressions) => {
+            symbols.push_level();
+
+            let mut type_var = Type::Unit;
+            for expression in expressions {
+                type_var = type_check(expression, symbols);
+            }
+
+            symbols.remove_level();
+            type_var
+        }
     }
 }
 
@@ -43,9 +169,6 @@ mod tests {
 
         let result = get_type("var a = true;");
         assert_eq!(result, Unit);
-
-        let result = get_type("+");
-        assert_eq!(result, Func(vec![Int, Int], Box::new(Int)));
     }
 
     #[test]
@@ -87,6 +210,12 @@ mod tests {
         get_type("var a = 1; a = true");
     }
 
+    #[test]
+    #[should_panic]
+    fn test_assign_non_var() {
+        get_type("1 = 2");
+    }
+
     #[test]
     fn test_operators() {
         let result = get_type("true or false");
diff --git a/src/compiler/variable.rs b/src/compiler/variable.rs
index bb4f925..2f565f0 100644
--- a/src/compiler/variable.rs
+++ b/src/compiler/variable.rs
@@ -1,6 +1,6 @@
 use std::fmt;
 
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq, Debug, Clone)]
 pub enum Type {
     Int,
     Bool,