diff --git a/runtime/arch.hpp b/runtime/arch.hpp
index 5443a62..33291b4 100644
--- a/runtime/arch.hpp
+++ b/runtime/arch.hpp
@@ -7,31 +7,42 @@ namespace sliger {
 // NOTICE: keep up to date with src/arch.ts
 
 enum class Op : uint32_t {
-    Nop = 0,
-    PushNull = 1,
-    PushInt = 2,
-    PushBool = 3,
-    PushString = 4,
-    PushPtr = 5,
-    Pop = 6,
-    LoadLocal = 7,
-    StoreLocal = 8,
-    Call = 9,
-    Return = 10,
-    Jump = 11,
-    JumpIfFalse = 12,
-    Add = 13,
-    Subtract = 14,
-    Multiply = 15,
-    Divide = 16,
-    Remainder = 17,
-    Equal = 18,
-    LessThan = 19,
-    And = 20,
-    Or = 21,
-    Xor = 22,
-    Not = 23,
-    SourceMap = 24,
+    Nop = 0x00,
+    PushNull = 0x01,
+    PushInt = 0x02,
+    PushBool = 0x03,
+    PushString = 0x04,
+    PushPtr = 0x05,
+    Pop = 0x06,
+    ReserveStatic = 0x07,
+    LoadStatic = 0x08,
+    StoreStatic = 0x09,
+    LoadLocal = 0x0a,
+    StoreLocal = 0x0b,
+    Call = 0x0c,
+    Return = 0x0d,
+    Jump = 0x0e,
+    JumpIfTrue = 0x0f,
+    Builtin = 0x10,
+    Add = 0x20,
+    Subtract = 0x21,
+    Multiply = 0x22,
+    Divide = 0x23,
+    Remainder = 0x24,
+    Equal = 0x25,
+    LessThan = 0x26,
+    And = 0x27,
+    Or = 0x28,
+    Xor = 0x29,
+    Not = 0x2a,
+    SourceMap = 0x30,
+};
+
+enum class Builtin : uint32_t {
+    StringConcat = 0x10,
+    StringEqual = 0x11,
+    ArraySet = 0x20,
+    StructSet = 0x30,
 };
 
 }
diff --git a/runtime/vm.cpp b/runtime/vm.cpp
index d24c279..6d903dc 100644
--- a/runtime/vm.cpp
+++ b/runtime/vm.cpp
@@ -37,8 +37,8 @@ inline auto maybe_op_to_string(uint32_t value) -> std::string
             return "Return";
         case Op::Jump:
             return "Jump";
-        case Op::JumpIfFalse:
-            return "JumpIfFalse";
+        case Op::JumpIfTrue:
+            return "JumpIfTrue";
         case Op::Add:
             return "Add";
         case Op::Subtract:
@@ -87,8 +87,8 @@ void VM::run_n_instructions(size_t amount)
 
 void VM::run_instruction()
 {
-    std::cout << std::format("    {:>4}: {:<12}{}\n", this->pc,
-        maybe_op_to_string(this->program[this->pc]), stack_repr_string(4));
+    /*std::cout << std::format("    {:>4}: {:<12}{}\n", this->pc,*/
+    /*    maybe_op_to_string(this->program[this->pc]), stack_repr_string(4));*/
     auto op = eat_op();
     switch (op) {
         case Op::Nop:
@@ -132,7 +132,28 @@ void VM::run_instruction()
             this->stack.pop_back();
             break;
         }
+        case Op::ReserveStatic: {
+            assert_program_has(1);
+            auto value = eat_uint32();
+            this->statics.reserve(value);
+            break;
+        }
+        case Op::LoadStatic: {
+            assert_program_has(1);
+            auto loc = eat_uint32();
+            auto value = this->statics.at(loc);
+            stack_push(value);
+            break;
+        }
+        case Op::StoreStatic: {
+            assert_program_has(1);
+            auto loc = eat_uint32();
+            auto value = stack_pop();
+            this->statics.at(loc) = value;
+            break;
+        }
         case Op::LoadLocal: {
+            assert_program_has(1);
             auto loc = eat_uint32();
             assert_fn_stack_has(loc);
             auto value = fn_stack_at(loc);
@@ -140,6 +161,7 @@ void VM::run_instruction()
             break;
         }
         case Op::StoreLocal: {
+            assert_program_has(1);
             auto loc = eat_uint32();
             assert_fn_stack_has(loc + 1);
             auto value = stack_pop();
@@ -187,15 +209,21 @@ void VM::run_instruction()
             this->pc = addr.as_ptr().value;
             break;
         }
-        case Op::JumpIfFalse: {
+        case Op::JumpIfTrue: {
             assert_stack_has(2);
             auto addr = stack_pop();
             auto cond = stack_pop();
-            if (!cond.as_bool().value) {
+            if (cond.as_bool().value) {
                 this->pc = addr.as_ptr().value;
             }
             break;
         }
+        case Op::Builtin: {
+            assert_program_has(1);
+            auto builtin_id = eat_uint32();
+            run_builtin(static_cast<Builtin>(builtin_id));
+            break;
+        }
         case Op::Add: {
             assert_stack_has(2);
             auto right = stack_pop().as_int().value;
@@ -296,3 +324,36 @@ void VM::run_instruction()
     }
     this->instruction_counter += 1;
 }
+
+void VM::run_builtin(Builtin builtin_id)
+{
+    switch (builtin_id) {
+        case Builtin::StringConcat: {
+            assert_stack_has(2);
+            auto right = stack_pop();
+            auto left = stack_pop();
+            stack_push(
+                String(right.as_string().value + left.as_string().value));
+            break;
+        }
+        case Builtin::StringEqual: {
+            assert_stack_has(2);
+            auto right = stack_pop();
+            auto left = stack_pop();
+            stack_push(Bool(right.as_string().value == left.as_string().value));
+            break;
+        }
+        case Builtin::ArraySet: {
+            assert_stack_has(2);
+            std::cerr << std::format("not implemented\n");
+            std::exit(1);
+            break;
+        }
+        case Builtin::StructSet: {
+            assert_stack_has(2);
+            std::cerr << std::format("not implemented\n");
+            std::exit(1);
+            break;
+        }
+    }
+}
diff --git a/runtime/vm.hpp b/runtime/vm.hpp
index 0ade960..c05d4fa 100644
--- a/runtime/vm.hpp
+++ b/runtime/vm.hpp
@@ -191,6 +191,8 @@ public:
     }
 
 private:
+    void run_builtin(Builtin builtin_id);
+
     inline void step() { this->pc += 1; }
 
     inline auto eat_op() -> Op
@@ -272,6 +274,7 @@ private:
     const uint32_t* program;
     size_t program_size;
     std::vector<Value> stack;
+    std::vector<Value> statics;
     heap::Heap heap;
     SourcePos current_pos = { 0, 1, 1 };
     int64_t instruction_counter = 0;