diff --git a/.fleet/run.json b/.fleet/run.json
new file mode 100644
index 0000000..dd0ce1f
--- /dev/null
+++ b/.fleet/run.json
@@ -0,0 +1,23 @@
+{
+    "configurations": [
+       {
+           "type": "command",
+           "name": "Compile",
+           "program": "bob"
+       },
+       {
+           "type": "command",
+           "name": "Run",
+           "program": "$PROJECT_DIR$/mx",
+           "workingDir": "$PROJECT_DIR$",
+           "args": ["test.mx"]
+       },
+       {
+           "type": "command",
+           "name": "Compile and run",
+           "program": "fish",
+           "workingDir": "$PROJECT_DIR$",
+           "args": ["test.fish"]
+       }
+    ]
+}
\ No newline at end of file
diff --git a/.fleet/settings.json b/.fleet/settings.json
new file mode 100644
index 0000000..17d0949
--- /dev/null
+++ b/.fleet/settings.json
@@ -0,0 +1,8 @@
+{
+    "plugins": [
+        {
+            "type": "add",
+            "pluginName": "fleet.vim"
+        }
+    ]
+}
\ No newline at end of file
diff --git a/mx b/mx
index 8f1f4ba..cf7cacb 100755
Binary files a/mx and b/mx differ
diff --git a/src/main.cpp b/src/main.cpp
index 04bfbe4..746662b 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -135,29 +135,49 @@ class SyntaxError {
     private:
     public:
         void fnTypeMismatch(string function, vector<string> validTypes, valtype typeGiven, string notes = "") {
-            cout << "TypeError: function type mismatch" << endl;
-            cout << "Function '" << function << "' expected one of the following types: ";
+            cerr << "TypeError: function type mismatch" << endl;
+            cerr << "Function '" << function << "' expected one of the following types: ";
             for (int i = 0; i < validTypes.size(); i++) {
-                if (i != 0) cout << ", ";
-                cout << validTypes[i];
+                if (i != 0) cerr << ", ";
+                cerr << validTypes[i];
             }
-            cout << endl << "Got type '";
-            if (typeGiven == valtype::INT) cout << "int";
-            else if (typeGiven == valtype::DEC) cout << "dec";
-            else if (typeGiven == valtype::STR) cout << "str";
-            else if (typeGiven == valtype::BOOL) cout << "bool";
-            else cout << "unknown";
-            cout << "' instead" << endl;
-            if (!notes.empty()) cout << "Notes: " << notes << endl;
+            cerr << endl << "Got type '";
+            if (typeGiven == valtype::INT) cerr << "int";
+            else if (typeGiven == valtype::DEC) cerr << "dec";
+            else if (typeGiven == valtype::STR) cerr << "str";
+            else if (typeGiven == valtype::BOOL) cerr << "bool";
+            else cerr << "unknown";
+            cerr << "' instead" << endl;
+            if (!notes.empty()) cerr << "Notes: " << notes << endl;
             exit(1);
         }
         void fnNotSufficientArgs(string function, int minArgs, int maxArgs, int argsGiven) {
-            cout << "TypeError: function not sufficient arguments" << endl;
-            cout << "Function '" << function << "' expected between " << minArgs << " and " << maxArgs << " arguments, got " << argsGiven << endl;
+            cerr << "TypeError: function not sufficient arguments" << endl;
+            cerr << "Function '" << function << "' expected between " << minArgs << " and " << maxArgs << " arguments, got " << argsGiven << endl;
             exit(1);
         }
         void unknownFn() {
-            cout << "TypeError: unknown function" << endl;
+            cerr << "TypeError: unknown function" << endl;
+            exit(1);
+        }
+        void mathTypeMismatch(string notes = "") {
+            cerr << "MathError: cannot add two different types together" << endl;
+            if (!notes.empty()) cerr << "Notes: " << notes << endl;
+            exit(1);
+        }
+        void mathTooFewArgs(string notes = "") {
+            cerr << "MathError: too few things to add together" << endl;
+            if (!notes.empty()) cerr << "Notes: " << notes << endl;
+            exit(1);
+        }
+        void mathCannotDoOperationOnType(string operatorUsed, string type, string notes = "") {
+            cerr << "MathError: cannot use operator '" + operatorUsed + " on type '" + type + "'" << endl;
+            if (!notes.empty()) cerr << "Notes: " << notes << endl;
+            exit(1);
+        }
+        void generalError(string notes = "") {
+            cerr << "GeneralError: Something went awfully wrong and we don't know why lmao" << endl;
+            if (!notes.empty()) cerr << "Notes: " << notes << endl;
             exit(1);
         }
 };
@@ -328,6 +348,7 @@ class Parser {
 
 class Interpreter {
     private:
+        SyntaxError syntaxError;
         vector<Token> tokens;
         map<string, Value> variables;
         Logger log;
@@ -380,6 +401,62 @@ class Interpreter {
                         }
                     }
                 }
+                // Do math
+                for (int i = 0; i < currentInstruction.size(); i++) {
+                    if (currentInstruction[i].keyword == keywords::ADD || currentInstruction[i].keyword == keywords::SUBTRACT || currentInstruction[i].keyword == keywords::MULTIPLY || currentInstruction[i].keyword == keywords::DIVIDE) {
+                        Token newToken;
+                        if (currentInstruction.size() < i + 1) syntaxError.mathTooFewArgs();
+                        Token before = currentInstruction[i - 1];
+                        Token after = currentInstruction[i + 1];
+                        if (before.type != after.type) syntaxError.mathTypeMismatch();
+                        newToken.type = before.type;
+                        if (currentInstruction[i].keyword == keywords::ADD) {
+                            if (newToken.type == valtype::INT) {
+                                newToken.value.value = get<int>(before.value.value) + get<int>(after.value.value);
+                            }
+                        else if (newToken.type == valtype::DEC) {
+                                newToken.value.value = get<double>(before.value.value) + get<double>(after.value.value);
+                            }
+                        else if (newToken.type == valtype::STR) {
+                                newToken.value.value = get<string>(before.value.value) + get<string>(after.value.value);
+                            } else {
+                                syntaxError.mathCannotDoOperationOnType("+", "bool");
+                            }
+                        }
+                    else if (currentInstruction[i].keyword == keywords::SUBTRACT) {
+                            if (newToken.type == valtype::INT) {
+                                newToken.value.value = get<int>(before.value.value) - get<int>(after.value.value);
+                            }
+                        else if (newToken.type == valtype::DEC) {
+                                newToken.value.value = get<double>(before.value.value) - get<double>(after.value.value);
+                            } else {
+                                syntaxError.mathCannotDoOperationOnType("-", "bool or string");
+                            }
+                        }
+                    else if (currentInstruction[i].keyword == keywords::MULTIPLY) {
+                            if (newToken.type == valtype::INT) {
+                                newToken.value.value = get<int>(before.value.value) * get<int>(after.value.value);
+                            }
+                        else if (newToken.type == valtype::DEC) {
+                                newToken.value.value = get<double>(before.value.value) * get<double>(after.value.value);
+                            } else {
+                                syntaxError.mathCannotDoOperationOnType("*", "bool or string");
+                            }
+                        }
+                    else if (currentInstruction[i].keyword == keywords::DIVIDE) {
+                            if (newToken.type == valtype::INT) {
+                                newToken.value.value = get<int>(before.value.value) / get<int>(after.value.value);
+                            }
+                        else if (newToken.type == valtype::DEC) {
+                                newToken.value.value = get<double>(before.value.value) / get<double>(after.value.value);
+                            } else {
+                                syntaxError.mathCannotDoOperationOnType("/", "bool or string");
+                            }
+                        } else {
+                            syntaxError.generalError("Da math aint mathing");
+                        }
+                    }
+                }
                 // Execute the instruction
                 executeCode(currentInstruction);
             }
diff --git a/test.fish b/test.fish
new file mode 100644
index 0000000..9e82140
--- /dev/null
+++ b/test.fish
@@ -0,0 +1,5 @@
+#!/usr/bin/fish
+
+bob
+
+./mx test.mx
\ No newline at end of file