diff --git a/.aiignore b/.aiignore
new file mode 100644
index 0000000..5682e0f
--- /dev/null
+++ b/.aiignore
@@ -0,0 +1,7 @@
+.DS_Store
+*.log
+*.tmp
+build/
+dist/
+out/
+tmp/
diff --git a/.gitignore b/.gitignore
index 0bbbad2..7cda0e8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,7 @@
+.idea/
+build/
+dist/
+out/
 src/*.o
 tmp/
 fun
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..2455fe8
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,52 @@
+cmake_minimum_required(VERSION 3.16)
+project(fun C)
+
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
+# Core VM/library sources
+add_library(fun_core
+        src/bytecode.c
+        src/value.c
+        src/vm.c
+)
+
+target_include_directories(fun_core PUBLIC
+        ${CMAKE_CURRENT_SOURCE_DIR}/src
+)
+
+# Playground / interpreter (future /usr/bin/fun)
+add_executable(fun
+        src/fun.c
+        examples/hello_world.fun
+)
+target_link_libraries(fun PRIVATE fun_core)
+
+# Internal test programs
+add_executable(fun_test 
+        src/fun_test.c
+)
+target_link_libraries(fun_test PRIVATE fun_core)
+
+add_executable(test_opcodes 
+        src/test_opcodes.c
+)
+target_link_libraries(test_opcodes PRIVATE fun_core)
+
+# Convenience targets for cleaning (optional)
+add_custom_target(clean-build
+        COMMAND ${CMAKE_COMMAND} --build ${CMAKE_BINARY_DIR} --target clean
+        COMMENT "Clean build outputs (objects, binaries) in the build directory"
+)
+add_custom_target(dist-clean
+        COMMAND ${CMAKE_COMMAND} --build ${CMAKE_BINARY_DIR} --target clean
+        COMMAND ${CMAKE_COMMAND} -E rm -rf
+        ${CMAKE_BINARY_DIR}/CMakeCache.txt
+        ${CMAKE_BINARY_DIR}/CMakeFiles
+        ${CMAKE_BINARY_DIR}/cmake_install.cmake
+        ${CMAKE_BINARY_DIR}/install_manifest.txt
+        ${CMAKE_BINARY_DIR}/Makefile
+        ${CMAKE_BINARY_DIR}/*.ninja
+        ${CMAKE_BINARY_DIR}/.ninja_*
+        COMMENT "Remove build outputs and CMake-generated files (reconfigure needed)"
+)
diff --git a/examples/hello_world.fun b/examples/hello_world.fun
new file mode 100755
index 0000000..4c9d305
--- /dev/null
+++ b/examples/hello_world.fun
@@ -0,0 +1,5 @@
+#!/usr/bin/env fun
+
+fun hello_world() {
+  print("Hello, world!")
+}
diff --git a/draft.fun b/spec/draft.fun
similarity index 100%
rename from draft.fun
rename to spec/draft.fun
diff --git a/src/bytecode.c b/src/bytecode.c
index 5ac8ad9..062604b 100644
--- a/src/bytecode.c
+++ b/src/bytecode.c
@@ -41,3 +41,56 @@ void bytecode_free(Bytecode *bc) {
     free(bc);
 }
 
+static const char *opcode_name(OpCode op) {
+    switch (op) {
+        case OP_NOP: return "NOP";
+        case OP_LOAD_CONST: return "LOAD_CONST";
+        case OP_LOAD_LOCAL: return "LOAD_LOCAL";
+        case OP_STORE_LOCAL: return "STORE_LOCAL";
+        case OP_LOAD_GLOBAL: return "LOAD_GLOBAL";
+        case OP_STORE_GLOBAL: return "STORE_GLOBAL";
+        case OP_ADD: return "ADD";
+        case OP_SUB: return "SUB";
+        case OP_MUL: return "MUL";
+        case OP_DIV: return "DIV";
+        case OP_LT: return "LT";
+        case OP_LTE: return "LTE";
+        case OP_GT: return "GT";
+        case OP_GTE: return "GTE";
+        case OP_EQ: return "EQ";
+        case OP_NEQ: return "NEQ";
+        case OP_POP: return "POP";
+        case OP_JUMP: return "JUMP";
+        case OP_JUMP_IF_FALSE: return "JUMP_IF_FALSE";
+        case OP_CALL: return "CALL";
+        case OP_RETURN: return "RETURN";
+        case OP_PRINT: return "PRINT";
+        case OP_HALT: return "HALT";
+        case OP_MOD: return "MOD";
+        case OP_AND: return "AND";
+        case OP_OR: return "OR";
+        case OP_NOT: return "NOT";
+        case OP_DUP: return "DUP";
+        case OP_SWAP: return "SWAP";
+        default: return "???";
+    }
+}
+
+void bytecode_dump(const Bytecode *bc) {
+    if (!bc) {
+        printf("<null bytecode>\n");
+        return;
+    }
+    printf("Constants (%d):\n", bc->const_count);
+    for (int i = 0; i < bc->const_count; ++i) {
+        printf("  [%d] ", i);
+        print_value(&bc->constants[i]);
+        printf("\n");
+    }
+    printf("Instructions (%d):\n", bc->instr_count);
+    for (int i = 0; i < bc->instr_count; ++i) {
+        const Instruction *ins = &bc->instructions[i];
+        printf("  %3d: %-15s %d\n", i, opcode_name(ins->op), ins->operand);
+    }
+}
+
diff --git a/src/bytecode.h b/src/bytecode.h
index 108035d..3e705cc 100644
--- a/src/bytecode.h
+++ b/src/bytecode.h
@@ -66,5 +66,8 @@ int bytecode_add_instruction(Bytecode *bc, OpCode op, int32_t operand);
 void bytecode_set_operand(Bytecode *bc, int idx, int32_t operand); /* patching */
 void bytecode_free(Bytecode *bc);
 
+// utilities
+void bytecode_dump(const Bytecode *bc);
+
 #endif
 
diff --git a/src/fun_test.c b/src/fun_test.c
new file mode 100644
index 0000000..892a166
--- /dev/null
+++ b/src/fun_test.c
@@ -0,0 +1,133 @@
+#include "bytecode.h"
+#include "value.h"
+#include "vm.h"
+#include <stdio.h>
+
+#define ASSERT_EQ(val, expected) \
+    if ((val).type != VAL_INT || (val).i != (expected)) { \
+        fprintf(stderr, "Assertion failed: expected %lld, got ", (long long)(expected)); \
+        print_value(&(val)); \
+        printf("\n"); \
+        return 1; \
+    }
+
+int main(void) {
+    VM vm;
+    vm_init(&vm);
+
+    Bytecode *bc = bytecode_new();
+
+    // constants
+    int c0 = bytecode_add_constant(bc, make_int(0));
+    int c1 = bytecode_add_constant(bc, make_int(1));
+    int c2 = bytecode_add_constant(bc, make_int(2));
+    int c3 = bytecode_add_constant(bc, make_int(3));
+    int c10 = bytecode_add_constant(bc, make_int(10));
+    int c42 = bytecode_add_constant(bc, make_int(42));
+
+    // ---------- Arithmetic ----------
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c42);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_ADD, 0);        // 42+1=43
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c10);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c3);
+    bytecode_add_instruction(bc, OP_SUB, 0);        // 10-3=7
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c3);
+    bytecode_add_instruction(bc, OP_MUL, 0);        // 2*3=6
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c10);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_DIV, 0);        // 10/2=5
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c10);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c3);
+    bytecode_add_instruction(bc, OP_MOD, 0);        // 10%3=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    // ---------- Comparisons ----------
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LT, 0);         // 1<2=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LTE, 0);        // 2<=2=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c3);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_GT, 0);         // 3>2=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_GTE, 0);        // 2>=2=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_EQ, 0);         // 2==2=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c3);
+    bytecode_add_instruction(bc, OP_NEQ, 0);        // 2!=3=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    // ---------- Logical ----------
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c0);
+    bytecode_add_instruction(bc, OP_AND, 0);        // 1&&0=0
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c0);
+    bytecode_add_instruction(bc, OP_OR, 0);         // 1||0=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c0);
+    bytecode_add_instruction(bc, OP_NOT, 0);        // !0=1
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    // ---------- Stack ----------
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_DUP, 0);        // duplicate 1
+    bytecode_add_instruction(bc, OP_ADD, 0);        // 1+1=2
+    bytecode_add_instruction(bc, OP_PRINT, 0);
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
+    bytecode_add_instruction(bc, OP_SWAP, 0);       // swap top two
+    bytecode_add_instruction(bc, OP_PRINT, 0);      // top=1
+
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_POP, 0);        // discard 1 (stack now empty)
+
+    // ---------- HALT ----------
+    bytecode_add_instruction(bc, OP_HALT, 0);
+
+    printf("=== Bytecode dump ===\n");
+    for (int i = 0; i < bc->instr_count; ++i) {
+        Instruction instr = bc->instructions[i];
+        printf("instr %3d: opcode=%2d operand=%d\n", i, instr.op, instr.operand);
+    }
+    printf("=====================\n");
+
+    // run VM
+    vm_run(&vm, bc);
+
+    printf("All tests executed. Output count: %d\n", vm.output_count);
+
+    vm_clear_output(&vm);
+    bytecode_free(bc);
+    return 0;
+}
+
diff --git a/src/test_opcodes.c b/src/test_opcodes.c
index 2914857..541c2a3 100644
--- a/src/test_opcodes.c
+++ b/src/test_opcodes.c
@@ -4,33 +4,40 @@
 #include <stdio.h>
 
 int main() {
+
+    VM vm;
+    vm_init(&vm);
+    
     Bytecode *bc = bytecode_new();
 
     // Example: test OP_ADD
     int c1 = bytecode_add_constant(bc, make_int(5));
     int c2 = bytecode_add_constant(bc, make_int(3));
-    bytecode_add_instruction(bc, OP_CONSTANT, c1);
-    bytecode_add_instruction(bc, OP_CONSTANT, c2);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c1);
+    bytecode_add_instruction(bc, OP_LOAD_CONST, c2);
     bytecode_add_instruction(bc, OP_ADD, 0);
     bytecode_add_instruction(bc, OP_PRINT, 0);
 
-    VM vm;
-    vm_init(&vm);
-
     printf("=== Bytecode dump ===\n");
-    bytecode_dump(bc);
-
-    if (vm_run(&vm, bc) != 0) {
-        printf("Runtime error!\n");
+    for (int i = 0; i < bc->instr_count; ++i) {
+        Instruction instr = bc->instructions[i];
+        printf("instr %3d: opcode=%2d operand=%d\n", i, instr.op, instr.operand);
     }
+    printf("=====================\n");
+    bytecode_dump(bc);
+    printf("=====================\n");
+    
+    vm_run(&vm, bc);
 
     printf("Output count: %d\n", vm.output_count);
     for (int i = 0; i < vm.output_count; i++) {
-        printf("Output[%d] = %ld\n", i, vm.output[i].i);
+        printf("Output[%d] = ", i);
+        print_value(&vm.output[i]);
+        printf("\n");
     }
 
+    vm_clear_output(&vm);
     vm_free(&vm);
     bytecode_free(bc);
     return 0;
 }
-
diff --git a/src/vm.c b/src/vm.c
index 9e34ecf..7c7925d 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -3,6 +3,7 @@
 #include "value.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 void vm_clear_output(VM *vm) {
     for (int i = 0; i < vm->output_count; ++i) {
@@ -259,7 +260,29 @@ void vm_run(VM *vm, Bytecode *entry) {
             case OP_EQ: {
                 Value b = pop_value(vm);
                 Value a = pop_value(vm);
-                push_value(vm, make_int((a.type == b.type && a.i == b.i) ? 1 : 0)); // for ints only, extend later
+                int eq = 0;
+                if (a.type == b.type) {
+                    switch (a.type) {
+                        case VAL_INT:
+                            eq = (a.i == b.i);
+                            break;
+                        case VAL_STRING:
+                            eq = (a.s && b.s) ? (strcmp(a.s, b.s) == 0) : (a.s == b.s);
+                            break;
+                        case VAL_FUNCTION:
+                            eq = (a.fn == b.fn);
+                            break;
+                        case VAL_NIL:
+                            eq = 1;
+                            break;
+                        default:
+                            eq = 0;
+                            break;
+                    }
+                } else {
+                    eq = 0;
+                }
+                push_value(vm, make_int(eq ? 1 : 0));
                 free_value(a); free_value(b);
                 break;
             }
@@ -267,11 +290,34 @@ void vm_run(VM *vm, Bytecode *entry) {
             case OP_NEQ: {
                 Value b = pop_value(vm);
                 Value a = pop_value(vm);
-                push_value(vm, make_int((a.type != b.type || a.i != b.i) ? 1 : 0)); // for ints only
+                int neq = 1;
+                if (a.type == b.type) {
+                    switch (a.type) {
+                        case VAL_INT:
+                            neq = (a.i != b.i);
+                            break;
+                        case VAL_STRING:
+                            neq = (a.s && b.s) ? (strcmp(a.s, b.s) != 0) : (a.s != b.s);
+                            break;
+                        case VAL_FUNCTION:
+                            neq = (a.fn != b.fn);
+                            break;
+                        case VAL_NIL:
+                            neq = 0;
+                            break;
+                        default:
+                            neq = 1;
+                            break;
+                    }
+                } else {
+                    neq = 1;
+                }
+                push_value(vm, make_int(neq ? 1 : 0));
                 free_value(a); free_value(b);
                 break;
             }
 
+
             case OP_JUMP_IF_FALSE: {
                 Value cond = pop_value(vm);
                 int truthy = value_is_truthy(&cond);