diff --git a/Makefile b/Makefile
index a803ee3..ccb5783 100644
--- a/Makefile
+++ b/Makefile
@@ -21,7 +21,7 @@ BASE_CFLAGS   := -I$(SRC_DIR) -Wall -Wextra -Werror -pedantic
 CORE_CFLAGS   := $(BASE_CFLAGS) -std=c89 -ffreestanding -nostdlib -fno-builtin
 
 # --- PLATFORM-SPECIFIC FLAGS ---
-PLATFORM_CFLAGS := $(BASE_CFLAGS)
+PLATFORM_CFLAGS := $(BASE_CFLAGS) -std=c99
 
 # --- MODE & PLATFORM SPECIFIC FLAGS ---
 ifeq ($(BUILD_MODE), deploy)
@@ -51,8 +51,8 @@ ifeq ($(PLATFORM), emscripten)
 
     # For deploy: optimize, strip debug, minimize size
     ifeq ($(BUILD_MODE), deploy)
-        PLATFORM_CFLAGS += -O3
-        LDFLAGS         += -O3 --closure 1
+        PLATFORM_CFLAGS += -O2
+        LDFLAGS         += -O2 --closure 1
     else
         # For debug: preserve names, generate source maps
         PLATFORM_CFLAGS += -gsource-map
@@ -68,23 +68,28 @@ ifndef TARGET
     TARGET = $(BUILD_DIR)/zre-$(PLATFORM)$(TARGET_SUFFIX)
 endif
 
-# --- CORE SOURCES (flat in src/) ---
-CORE_SOURCES := \
-	$(SRC_DIR)/str.c \
-	$(SRC_DIR)/vm.c \
-	$(SRC_DIR)/device.c \
-	$(SRC_DIR)/test.c
+# --- VM CORE SOURCES ---
+VM_SOURCES := \
+	$(SRC_DIR)/vm/vm.c \
+	$(SRC_DIR)/vm/device.c \
+	$(SRC_DIR)/vm/str.c
 
-# --- PLATFORM SOURCE ---
-PLATFORM_SOURCE := $(ARCH_DIR)/main.c \
-     $(ARCH_DIR)/devices.c 
+ifeq ($(BUILD_MODE), deploy)
+	PLATFORM_SOURCE := $(ARCH_DIR)/main.c \
+		$(ARCH_DIR)/devices.c
+else
+	PLATFORM_SOURCE := $(ARCH_DIR)/main.c \
+		$(ARCH_DIR)/devices.c \
+		$(SRC_DIR)/tools/test.c \
+        $(SRC_DIR)/tools/parser.c
+endif
 
 # --- OBJECT FILES ---
-CORE_OBJS := $(CORE_SOURCES:$(SRC_DIR)/%.c=$(BUILD_DIR)/%.o)
+VM_OBJS := $(VM_SOURCES:$(SRC_DIR)/%.c=$(BUILD_DIR)/%.o)
 PLATFORM_OBJ := $(PLATFORM_SOURCE:$(SRC_DIR)/%.c=$(BUILD_DIR)/%.o)
 
 # --- DEPENDENCIES ---
-DEPS := $(CORE_OBJS:.o=.d) $(PLATFORM_OBJ:.o=.d)
+DEPS := $(VM_OBJS:.o=.d) $(PLATFORM_OBJ:.o=.d)
 
 .PHONY: all debug deploy clean clean-all help
 
@@ -99,8 +104,23 @@ debug: $(TARGET)
 deploy: BUILD_MODE = deploy
 deploy: $(TARGET)
 
+# --- COMPILE VM CORE (freestanding) ---
+$(BUILD_DIR)/vm/%.o: $(SRC_DIR)/vm/%.c
+	@mkdir -p $(dir $@)
+	$(CC) $(CORE_CFLAGS) -MMD -MP -c $< -o $@
+
+# --- COMPILE TOOLS (debug only, uses PLATFORM_CFLAGS) ---
+$(BUILD_DIR)/tools/%.o: $(SRC_DIR)/tools/%.c
+	@mkdir -p $(dir $@)
+	$(CC) $(PLATFORM_CFLAGS) -MMD -MP -c $< -o $@
+
+# --- COMPILE PLATFORM ---
+$(BUILD_DIR)/arch/$(PLATFORM)/%.o: $(ARCH_DIR)/%.c
+	@mkdir -p $(dir $@)
+	$(CC) $(PLATFORM_CFLAGS) -MMD -MP -c $< -o $@
+
 # Main build rule
-$(TARGET): $(CORE_OBJS) $(PLATFORM_OBJ)
+$(TARGET): $(VM_OBJS) $(PLATFORM_OBJ)
 	@mkdir -p $(dir $@)
 	$(CC) $(PLATFORM_CFLAGS) $(LDFLAGS) -o $@ $^
 	@echo "Built: $@"
@@ -108,16 +128,6 @@ $(TARGET): $(CORE_OBJS) $(PLATFORM_OBJ)
 		echo "Open in browser: file://$(shell pwd)/$@"; \
 	fi
 
-# --- COMPILE CORE (freestanding) ---
-$(BUILD_DIR)/%.o: $(SRC_DIR)/%.c
-	@mkdir -p $(dir $@)
-	$(CC) $(CORE_CFLAGS) -MMD -MP -c $< -o $@
-
-# --- COMPILE PLATFORM ---
-$(BUILD_DIR)/arch/$(PLATFORM)/%.o: $(ARCH_DIR)/%.c
-	@mkdir -p $(dir $@)
-	$(CC) $(PLATFORM_CFLAGS) -MMD -MP -c $< -o $@
-
 # --- AUTO-DEPENDENCIES ---
 -include $(DEPS)
 
diff --git a/src/arch/linux/devices.h b/src/arch/linux/devices.h
index 845e6c0..376324a 100644
--- a/src/arch/linux/devices.h
+++ b/src/arch/linux/devices.h
@@ -1,5 +1,5 @@
-#include "../../device.h"
-#include "../../vm.h"
+#include "../../vm/device.h"
+#include "../../vm/vm.h"
 #include <SDL2/SDL.h>
 
 /* Screen device data */
diff --git a/src/arch/linux/main.c b/src/arch/linux/main.c
index 97f87bf..c5dc305 100644
--- a/src/arch/linux/main.c
+++ b/src/arch/linux/main.c
@@ -1,5 +1,6 @@
-#include "../../test.h"
-#include "../../vm.h"
+#include "../../tools/test.h"
+#include "../../tools/parser.h"
+#include "../../vm/vm.h"
 #include "devices.h"
 #include <SDL2/SDL.h>
 
@@ -12,19 +13,19 @@ static DeviceOps screen_ops = {.open = screen_open,
                                .read = screen_read,
                                .write = screen_write,
                                .close = screen_close,
-                               .ioctl = NULL};
+                               .ioctl = nil};
 
 static DeviceOps mouse_ops = {.open = mouse_open,
                               .read = mouse_read,
                               .write = mouse_write,
                               .close = mouse_close,
-                              .ioctl = NULL};
+                              .ioctl = nil};
 
 static DeviceOps keyboard_ops = {.open = keyboard_open,
                                  .read = keyboard_read,
                                  .write = keyboard_write,
                                  .close = keyboard_close,
-                                 .ioctl = NULL};
+                                 .ioctl = nil};
 
 static DeviceOps console_device_ops = {
     .open = console_open,
@@ -62,6 +63,28 @@ void compileFile(const char *path, VM *vm) {
 }
 
 void repl(VM *vm) {
+  USED(vm);
+
+  const char *source = "(fn main ()\n"
+                       "  (print (ftos (addf 1.0 2.0))))\n"
+                       "\n"
+                       "(device Terminal \"/dev/term/0\"\n"
+                       "  (write buffer size)\n"
+                       "  (read buffer size))";
+
+  printf("Parsing:\n%s\n\n", source);
+
+  ExprNode *ast = expr_parse(source, strlen(source));
+  if (!ast) {
+    printf("Parse failed.\n");
+    exit(1);
+  }
+
+  printf("AST:\n");
+  expr_print(ast, 0);
+
+  expr_free(ast);
+
   char line[1024];
   for (;;) {
     printf("> ");
@@ -70,25 +93,26 @@ void repl(VM *vm) {
       printf("\n");
       break;
     }
-    /* reset the code counter to 0 */
-    vm->cp = 0;
-    vm->sp = 0;
-    vm->pc = 0;
-    vm->mp = 0;
 
-    /* assemble(line, vm); */
-    while (step_vm(vm))
-      ;
+    ExprNode *ast = expr_parse(source, strlen(line));
+    if (!ast) {
+      printf("Parse failed.\n");
+      continue;
+    }
+
+    printf("AST:\n");
+    expr_print(ast, 0);
+
+    expr_free(ast);
   }
   exit(0);
 }
 
 enum FlagType {
   FLAG_NONE = 0,
-  FLAG_DEV_MODE = 1,
-  FLAG_TEST_MODE = 2,
-  FLAG_DUMP_ROM = 4,
-  FLAG_GUI_MODE = 8,
+  FLAG_TEST_MODE = 1,
+  FLAG_DUMP_ROM = 2,
+  FLAG_GUI_MODE = 4,
 };
 
 #define MAX_INPUT_FILES 16 /* Adjust based on your system's constraints */
@@ -114,9 +138,7 @@ i32 parse_arguments(i32 argc, char *argv[], struct CompilerConfig *config) {
   for (i = 1; i < argc; i++) {
     if (argv[i][0] == '-') {
       /* Long and short flag handling */
-      if (strcmp(argv[i], "-d") == 0 || strcmp(argv[i], "--dev") == 0) {
-        config->flags |= FLAG_DEV_MODE;
-      } else if (strcmp(argv[i], "-g") == 0 || strcmp(argv[i], "--gui") == 0) {
+      if (strcmp(argv[i], "-g") == 0 || strcmp(argv[i], "--gui") == 0) {
         config->flags |= FLAG_GUI_MODE;
       } else if (strcmp(argv[i], "-t") == 0 || strcmp(argv[i], "--test") == 0) {
         config->flags |= FLAG_TEST_MODE;
diff --git a/src/gen/build.sh b/src/gen/build.sh
index bdf5a10..b758b83 100644
--- a/src/gen/build.sh
+++ b/src/gen/build.sh
@@ -1,2 +1,2 @@
 gcc math_gen.c -o math_gen -lm
-./math_gen > ../math.h
\ No newline at end of file
+./math_gen > ./math.h
\ No newline at end of file
diff --git a/src/tools/parser.c b/src/tools/parser.c
new file mode 100644
index 0000000..12508c8
--- /dev/null
+++ b/src/tools/parser.c
@@ -0,0 +1,194 @@
+#include "parser.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+// Helper function to allocate memory and handle errors
+static void *safe_malloc(size_t size) {
+    void *ptr = malloc(size);
+    if (!ptr) {
+        fprintf(stderr, "Memory allocation failed\n");
+        exit(1);
+    }
+    return ptr;
+}
+
+// Helper function to create a new node
+static ExprNode *expr_node_create(const char *token, int line) {
+    ExprNode *node = (ExprNode *)safe_malloc(sizeof(ExprNode));
+    node->token = strdup(token ? token : "");
+    node->children = NULL;
+    node->child_count = 0;
+    node->line = line;
+    return node;
+}
+
+// Forward declaration
+static ExprNode *parse_expression(const char **ptr, int line);
+
+// Skip whitespace characters
+static const char *skip_whitespace(const char *ptr) {
+    while (*ptr && isspace(*ptr)) {
+        ptr++;
+    }
+    return ptr;
+}
+
+// Parse a token (atom)
+static char *parse_token(const char **ptr) {
+    const char *start = *ptr;
+    
+    // Skip leading whitespace
+    start = skip_whitespace(start);
+    if (!*start) return NULL;
+    
+    const char *end = start;
+    
+    // Handle parentheses specially
+    if (*end == '(' || *end == ')') {
+        end++;
+    } else {
+        // Read until whitespace or parentheses
+        while (*end && !isspace(*end) && *end != '(' && *end != ')') {
+            end++;
+        }
+    }
+    
+    if (end == start) return NULL;
+    
+    size_t len = end - start;
+    char *token = (char *)safe_malloc(len + 1);
+    memcpy(token, start, len);
+    token[len] = '\0';
+    
+    *ptr = end;
+    return token;
+}
+
+// Parse a list (expression starting with '(')
+static ExprNode *parse_list(const char **ptr, int line) {
+    // Skip the opening parenthesis
+    (*ptr)++;
+    
+    // Parse the operator (first token)
+    *ptr = skip_whitespace(*ptr);
+    if (**ptr == ')') {
+        // Empty list
+        (*ptr)++;
+        return expr_node_create("nil", line);
+    }
+    
+    // Parse the operator/first element
+    char *op_token = parse_token(ptr);
+    if (!op_token) {
+        fprintf(stderr, "Error: Expected operator at line %d\n", line);
+        return NULL;
+    }
+    
+    ExprNode *node = expr_node_create(op_token, line);
+    free(op_token);
+    
+    // Parse children
+    while (**ptr && **ptr != ')') {
+        *ptr = skip_whitespace(*ptr);
+        if (**ptr == ')') break;
+        
+        ExprNode *child = parse_expression(ptr, line);
+        if (child) {
+            // Resize children array properly
+            ExprNode **new_children = (ExprNode **)safe_malloc(sizeof(ExprNode *) * (node->child_count + 1));
+            
+            // Copy existing children
+            for (size_t i = 0; i < node->child_count; i++) {
+                new_children[i] = node->children[i];
+            }
+            
+            // Add new child
+            new_children[node->child_count] = child;
+            
+            // Free old array and update
+            free(node->children);
+            node->children = new_children;
+            node->child_count++;
+        }
+        
+        *ptr = skip_whitespace(*ptr);
+    }
+    
+    if (**ptr == ')') {
+        (*ptr)++; // Skip closing parenthesis
+    } else {
+        fprintf(stderr, "Error: Missing closing parenthesis at line %d\n", line);
+    }
+    
+    return node;
+}
+
+// Parse an expression (either atom or list)
+static ExprNode *parse_expression(const char **ptr, int line) {
+    *ptr = skip_whitespace(*ptr);
+    
+    if (!**ptr) return NULL;
+    
+    if (**ptr == '(') {
+        return parse_list(ptr, line);
+    } else {
+        // Parse atom
+        char *token = parse_token(ptr);
+        if (token) {
+            ExprNode *node = expr_node_create(token, line);
+            free(token);
+            return node;
+        }
+        return NULL;
+    }
+}
+
+// Main parsing function
+ExprNode *expr_parse(const char *source, size_t source_len) {
+    if (!source || source_len == 0) return NULL;
+    
+    const char *ptr = source;
+    int line = 1;
+    
+    ptr = skip_whitespace(ptr);
+    if (!*ptr) return NULL;
+    
+    return parse_expression(&ptr, line);
+}
+
+// Free an Expr AST (and all children)
+void expr_free(ExprNode *node) {
+    if (!node) return;
+    
+    free(node->token);
+    
+    for (size_t i = 0; i < node->child_count; i++) {
+        expr_free(node->children[i]);
+    }
+    free(node->children);
+    free(node);
+}
+
+// Debug: print AST (for dev)
+void expr_print(ExprNode *node, int indent) {
+    if (!node) return;
+    
+    for (int i = 0; i < indent; i++) {
+        printf("  ");
+    }
+    
+    if (node->child_count == 0) {
+        // Atom
+        printf("Atom: '%s' (line %d)\n", node->token, node->line);
+    } else {
+        // List
+        printf("List: '%s' (line %d) [%zu children]\n", 
+               node->token, node->line, node->child_count);
+        
+        for (size_t i = 0; i < node->child_count; i++) {
+            expr_print(node->children[i], indent + 1);
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/tools/parser.h b/src/tools/parser.h
new file mode 100644
index 0000000..a58bd1c
--- /dev/null
+++ b/src/tools/parser.h
@@ -0,0 +1,27 @@
+#ifndef PARSER_H
+#define PARSER_H
+
+#include <stddef.h>  // for size_t
+
+// Forward declare
+typedef struct ExprNode ExprNode;
+
+// Node type: atom or list
+struct ExprNode {
+    char *token;           // For atoms: the value ("123", "$0", "add")
+                       // For lists: the operator (first token)
+    ExprNode **children;   // Array of child nodes (NULL if atom)
+    size_t child_count;    // 0 if atom
+    int line;              // Source line number (for errors)
+};
+
+// Parse a string into an Expr AST
+ExprNode *expr_parse(const char *source, size_t source_len);
+
+// Free an Expr AST (and all children)
+void expr_free(ExprNode *node);
+
+// Debug: print AST (for dev)
+void expr_print(ExprNode *node, int indent);
+
+#endif
\ No newline at end of file
diff --git a/src/test.c b/src/tools/test.c
similarity index 93%
rename from src/test.c
rename to src/tools/test.c
index cd312ca..05fcf81 100644
--- a/src/test.c
+++ b/src/tools/test.c
@@ -1,7 +1,7 @@
 #include "test.h"
-#include "opcodes.h"
-#include "str.h"
-#include "vm.h"
+#include "../vm/opcodes.h"
+#include "../vm/vm.h"
+#include "string.h"
 #include <stdint.h>
 
 u32 real_alloc(VM *vm, float v) {
@@ -39,7 +39,7 @@ struct TestMapping internal_tests[] = {
 bool compile_internal_test(const char *filename, VM *vm) {
   i32 i;
   for (i = 0; internal_tests[i].filename != NULL; i++) {
-    if (streq(internal_tests[i].filename, filename)) {
+    if (strcmp(internal_tests[i].filename, filename) == 0) {
       return internal_tests[i].test_func(vm);
     }
   }
diff --git a/src/test.h b/src/tools/test.h
similarity index 95%
rename from src/test.h
rename to src/tools/test.h
index 7cf5d2c..f3e33bf 100644
--- a/src/test.h
+++ b/src/tools/test.h
@@ -1,7 +1,7 @@
 #ifndef ZRE_TEST_H
 #define ZRE_TEST_H
 
-#include "opcodes.h"
+#include "../vm/opcodes.h"
 
 #define AS_FIXED(v)  ((float)(i32)(v) / 65536.0f)
 #define TO_FIXED(f)  ((u32)((i32)( \
diff --git a/src/common.h b/src/vm/common.h
similarity index 100%
rename from src/common.h
rename to src/vm/common.h
diff --git a/src/device.c b/src/vm/device.c
similarity index 100%
rename from src/device.c
rename to src/vm/device.c
diff --git a/src/device.h b/src/vm/device.h
similarity index 100%
rename from src/device.h
rename to src/vm/device.h
diff --git a/src/opcodes.h b/src/vm/opcodes.h
similarity index 100%
rename from src/opcodes.h
rename to src/vm/opcodes.h
diff --git a/src/str.c b/src/vm/str.c
similarity index 97%
rename from src/str.c
rename to src/vm/str.c
index 19ed6d8..c0b805f 100644
--- a/src/str.c
+++ b/src/vm/str.c
@@ -25,7 +25,7 @@ bool streq(const char *s1, const char *s2) {
 }
 
 
-u32 strlen(const char *str) {
+u32 strlength(const char *str) {
     u32 i;
     if (str == nil) {return 0;}
     for (i = 0; str[i] != '\0'; i++) {
@@ -34,7 +34,7 @@ u32 strlen(const char *str) {
     return i;
 }
 
-u32 strnlen(const char *str, u32 max_len) {
+u32 strnlength(const char *str, u32 max_len) {
     u32 i;
     if (str == nil) {return 0;}
     for (i = 0; i < max_len && str[i] != '\0'; i++) {
diff --git a/src/str.h b/src/vm/str.h
similarity index 67%
rename from src/str.h
rename to src/vm/str.h
index 460abee..684756c 100644
--- a/src/str.h
+++ b/src/vm/str.h
@@ -3,10 +3,11 @@
 
 #include "common.h"
 
-i32 strcopy(char* to, const char *from, u32 length);
-u32 strlen(const char* str);
 bool streq(const char *s1, const char *s2);
-char *write_digits_backwards(u32 value, char *buf_end, char *buf_start);
+i32 strcopy(char* to, const char *from, u32 length);
+u32 strlength(const char *str);
+u32 strnlength(const char *str, u32 max_len);
+void uint_to_string(u32 value, char *buffer);
 void int_to_string(i32 value, char *buffer);
 void fixed_to_string(i32 value, char *buffer);
 
diff --git a/src/vm.c b/src/vm/vm.c
similarity index 98%
rename from src/vm.c
rename to src/vm/vm.c
index 187b293..177d7bd 100644
--- a/src/vm.c
+++ b/src/vm/vm.c
@@ -434,7 +434,7 @@ bool step_vm(VM *vm) {
     src1 = read_u8(vm, code, vm->pc);
     vm->pc++;
     int_to_string(AS_INT(frame.registers[src1]), buffer);
-    ptr = str_alloc(vm, &frame, buffer, strlen(buffer));
+    ptr = str_alloc(vm, &frame, buffer, strlength(buffer));
     frame.registers[dest] = ptr;
     return true;
   }
@@ -445,7 +445,7 @@ bool step_vm(VM *vm) {
     src1 = read_u8(vm, code, vm->pc);
     vm->pc++;
     uint_to_string(frame.registers[src1], buffer);
-    ptr = str_alloc(vm, &frame, buffer, strlen(buffer));
+    ptr = str_alloc(vm, &frame, buffer, strlength(buffer));
     frame.registers[dest] = ptr;
     return true;
   }
@@ -457,7 +457,7 @@ bool step_vm(VM *vm) {
     vm->pc++;
     fixed_to_string(AS_INT(frame.registers[src1]), buffer);
     ptr =
-        str_alloc(vm, &frame, buffer, strlen(buffer)); /* copy buffer to dest */
+        str_alloc(vm, &frame, buffer, strlength(buffer)); /* copy buffer to dest */
     frame.registers[dest] = ptr;
     return true;
   }
diff --git a/src/vm.h b/src/vm/vm.h
similarity index 100%
rename from src/vm.h
rename to src/vm/vm.h