diff --git a/SLS_C/build.py b/SLS_C/build.py
deleted file mode 100644
index 24d8c67..0000000
--- a/SLS_C/build.py
+++ /dev/null
@@ -1,515 +0,0 @@
-#!/usr/bin/env python3
-import os
-import sys
-import subprocess
-from pathlib import Path
-import shutil
-import platform
-
-# ---------------------------------------------------------------------
-# CONFIG
-# ---------------------------------------------------------------------
-SRC_DIR = Path("src")
-TEST_DIR = Path("tests")
-OBJ_DIR = Path("obj")
-BIN_DIR = Path("bin")
-
-TARGET = BIN_DIR / "sls"
-TEST_TARGET = BIN_DIR / "sls_tests"
-
-# Platform-specific settings
-PICO_SDK_PATH = os.environ.get("PICO_SDK_PATH", Path.home() / "pico/pico-sdk")
-PICO_BUILD_DIR = Path("build_pico")
-PICO_TOOLCHAIN_PATH = Path("pico_arm_gcc_toolchain.cmake")
-
-# Unix gcc/clang flags
-COMMON_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Werror", "-Iinclude", "-g"]
-TEST_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Wno-unused-function", "-Werror",
-              "-Iinclude", "-g", "-O0"]
-
-# macOS-specific flags (for cross-compilation if needed)
-MACOS_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Werror", "-Iinclude", "-g",
-               "-mmacosx-version-min=10.13"]
-
-# Windows MSVC flags
-MSVC_FLAGS = ["/std:c11", "/Zi", "/Iinclude"]
-MSVC_TEST_FLAGS = MSVC_FLAGS + []
-
-# RP2040 toolchain file template
-PICO_TOOLCHAIN_TEMPLATE = """set(CMAKE_SYSTEM_NAME Generic)
-set(CMAKE_SYSTEM_PROCESSOR cortex-m0plus)
-
-# Specify the cross compiler
-set(CMAKE_C_COMPILER arm-none-eabi-gcc)
-set(CMAKE_CXX_COMPILER arm-none-eabi-g++)
-set(CMAKE_ASM_COMPILER arm-none-eabi-gcc)
-
-# Compiler flags for Cortex-M0+
-set(CMAKE_C_FLAGS_INIT "-mcpu=cortex-m0plus -mthumb")
-set(CMAKE_CXX_FLAGS_INIT "-mcpu=cortex-m0plus -mthumb")
-set(CMAKE_ASM_FLAGS_INIT "-mcpu=cortex-m0plus -mthumb")
-
-# Don't run the linker on compiler check
-set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
-
-# Adjust the default behavior of the FIND_XXX() commands:
-# search programs in the host environment
-set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
-
-# Search headers and libraries in the target environment
-set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
-set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
-"""
-
-# RP2040 settings
-RP2040_CMAKE_TEMPLATE = """cmake_minimum_required(VERSION 3.13)
-
-# Pico SDK initialization
-set(PICO_SDK_PATH "{pico_sdk_path}")
-include({pico_sdk_path}/external/pico_sdk_import.cmake)
-
-project({project_name} C CXX ASM)
-set(CMAKE_C_STANDARD 11)
-set(CMAKE_CXX_STANDARD 17)
-
-pico_sdk_init()
-
-# Main executable
-add_executable({project_name}
-{source_files}
-)
-
-# Set output name with .elf extension
-set_target_properties({project_name} PROPERTIES
-    OUTPUT_NAME "{project_name}.elf"
-    SUFFIX ""
-)
-
-# Add include directories
-target_include_directories({project_name} PRIVATE
-    ${{CMAKE_CURRENT_LIST_DIR}}/include
-)
-
-# Add compile definitions
-target_compile_definitions({project_name} PRIVATE
-    PICO_BUILD=1
-    GIT_COMMIT_HASH="{git_hash}"
-)
-
-# Link libraries
-target_link_libraries({project_name}
-    pico_stdlib
-    hardware_uart
-    hardware_gpio
-)
-
-# Enable USB/UART output
-pico_enable_stdio_usb({project_name} 1)
-pico_enable_stdio_uart({project_name} 1)
-
-# Create map/bin/hex/uf2 files
-pico_add_extra_outputs({project_name})
-"""
-
-# ---------------------------------------------------------------------
-# PLATFORM DETECTION
-# ---------------------------------------------------------------------
-def detect_platform():
-    """Detect the current operating system"""
-    system = platform.system()
-    if system == "Darwin":
-        return "macos"
-    elif system == "Windows":
-        return "windows"
-    elif system == "Linux":
-        return "linux"
-    return "unknown"
-
-PLATFORM = detect_platform()
-
-# ---------------------------------------------------------------------
-# COMPILER DETECTION
-# ---------------------------------------------------------------------
-def detect_compiler(target_platform=None):
-    """Detect appropriate compiler for the target platform"""
-    if target_platform == "rp2040":
-        return ("arm-none-eabi-gcc", "gcc")
-    
-    target = target_platform or PLATFORM
-    
-    if target == "windows" or os.name == "nt":
-        return ("cl", "msvc")
-    elif target == "macos":
-        # Prefer clang on macOS
-        if shutil.which("clang"):
-            return ("clang", "gcc")
-        return ("gcc", "gcc")
-    else:
-        return ("gcc", "gcc")
-
-CC, CC_KIND = detect_compiler()
-
-# ---------------------------------------------------------------------
-# PYTHON DETECTION
-# ---------------------------------------------------------------------
-def detect_python():
-    if os.name == "nt":
-        return "python"
-    return "python3"
-
-PYTHON = detect_python()
-
-
-# ---------------------------------------------------------------------
-# GIT COMMIT HASH
-# ---------------------------------------------------------------------
-def git_commit_hash():
-    try:
-        result_hash = subprocess.check_output(
-            ["git", "describe", "--always", "--dirty", "--abbrev=7"],
-            cwd=".",
-            stderr=subprocess.DEVNULL,
-            text=True
-        ).strip()
-        result_date = subprocess.check_output(
-            ["git", "show", "-s", "--format=%ci"],
-            cwd=".",
-            stderr=subprocess.DEVNULL,
-            text=True
-        ).strip()
-        return f"{result_hash} {result_date}"
-    except Exception:
-        return "unknown"
-
-
-GIT_HASH = git_commit_hash()
-
-
-# ---------------------------------------------------------------------
-# UTILS
-# ---------------------------------------------------------------------
-def mkdir(p: Path):
-    p.mkdir(parents=True, exist_ok=True)
-
-
-def run(cmd):
-    print(">>", " ".join(str(c) for c in cmd))
-    subprocess.check_call(cmd)
-
-
-def is_up_to_date(src, obj, dep):
-    if "meta" in [src.stem, obj.stem, dep.stem]:
-        return False
-    if not obj.exists():
-        return False
-    if dep.exists() and dep.stat().st_mtime > obj.stat().st_mtime:
-        return False
-    return src.stat().st_mtime < obj.stat().st_mtime
-
-
-# ---------------------------------------------------------------------
-# BUILD RULES
-# ---------------------------------------------------------------------
-def compile_source(src: Path, is_test=False, target_platform=None):
-    mkdir(OBJ_DIR)
-    obj = OBJ_DIR / (src.stem + ".o")
-    dep = OBJ_DIR / (src.stem + ".d")
-
-    if is_up_to_date(src, obj, dep):
-        return obj
-
-    compiler, kind = detect_compiler(target_platform)
-    
-    if kind == "msvc":
-        flags = MSVC_TEST_FLAGS if is_test else MSVC_FLAGS
-        cmd = [compiler] + flags + ["/Fo" + str(obj), "/c", str(src),
-                               f"/DGIT_COMMIT_HASH=\"{GIT_HASH}\""]
-    else:
-        if target_platform == "macos":
-            flags = MACOS_FLAGS if not is_test else TEST_FLAGS + ["-mmacosx-version-min=10.13"]
-        else:
-            flags = TEST_FLAGS if is_test else COMMON_FLAGS
-            
-        cmd = [compiler] + flags + [
-            f"-DGIT_COMMIT_HASH=\"{GIT_HASH}\"",
-            "-MMD", "-MP",
-            "-c", str(src), "-o", str(obj)
-        ]
-
-    run(cmd)
-    return obj
-
-
-def link_executable(objects, output: Path, target_platform=None):
-    mkdir(BIN_DIR)
-    compiler, kind = detect_compiler(target_platform)
-    
-    if kind == "msvc":
-        cmd = [compiler] + list(map(str, objects)) + ["/Fe" + str(output)]
-    else:
-        cmd = [compiler] + list(map(str, objects)) + ["-lm", "-o", str(output)]
-    run(cmd)
-
-
-# ---------------------------------------------------------------------
-# TEST CASE GENERATION
-# ---------------------------------------------------------------------
-def generate_tests():
-    script = Path("../SLS_Tests/yaml_to_c_tests.py")
-    yaml = Path("../SLS_Tests/cases.yaml")
-    out = TEST_DIR / "lexer_tests.c"
-
-    if not script.exists() or not yaml.exists():
-        print("Test generation skipped (missing files).")
-        return False
-
-    if out.exists() and out.stat().st_mtime > yaml.stat().st_mtime:
-        return True
-
-    run([PYTHON, str(script), str(yaml), str(out)])
-    return True
-
-
-# ---------------------------------------------------------------------
-# RP2040 BUILD
-# ---------------------------------------------------------------------
-def check_pico_sdk():
-    """Check if Pico SDK is available"""
-    sdk_path = Path(PICO_SDK_PATH)
-    if not sdk_path.exists():
-        print(f"ERROR: Pico SDK not found at {sdk_path}")
-        print("Please set PICO_SDK_PATH environment variable or install SDK at ~/pico/pico-sdk")
-        return False
-    
-    # Check for ARM toolchain
-    if not shutil.which("arm-none-eabi-gcc"):
-        print("ERROR: ARM toolchain not found!")
-        print("Please install arm-none-eabi-gcc:")
-        print("  Ubuntu/Debian: sudo apt install gcc-arm-none-eabi")
-        print("  macOS: brew install arm-none-eabi-gcc")
-        return False
-    
-    return True
-
-
-def generate_pico_toolchain():
-    """Generate ARM GCC toolchain file for CMake"""
-    with open(PICO_TOOLCHAIN_PATH, "w") as f:
-        f.write(PICO_TOOLCHAIN_TEMPLATE)
-    print(f"Generated {PICO_TOOLCHAIN_PATH}")
-
-
-def generate_pico_cmake(project_name="sls"):
-    """Generate CMakeLists.txt for RP2040 build"""
-    sources = list(SRC_DIR.glob("*.c"))
-    # Exclude main.c, repl.c, file.c and test files for Pico build
-    # pico_main.c will provide its own REPL implementation
-    sources = [s for s in sources 
-               if s.name not in ["main.c", "repl.c", "file.c"] 
-               and "test" not in s.stem.lower()]
-    
-    # Check for pico_main.c
-    pico_main = SRC_DIR / "pico_main.c"
-    if not pico_main.exists():
-        print(f"WARNING: {pico_main} not found! Please create it.")
-        print("The Pico build requires a pico_main.c file.")
-        return False
-    
-    sources.append(pico_main)
-    
-    source_files = "\n".join(f"    {s}" for s in sources)
-    
-    cmake_content = RP2040_CMAKE_TEMPLATE.format(
-        project_name=project_name,
-        source_files=source_files,
-        git_hash=GIT_HASH,
-        pico_sdk_path=PICO_SDK_PATH
-    )
-    
-    cmake_file = Path("CMakeLists.txt")
-    with open(cmake_file, "w") as f:
-        f.write(cmake_content)
-    
-    print(f"Generated {cmake_file}")
-    return True
-
-
-def build_rp2040():
-    """Build for RP2040 using CMake"""
-    if not check_pico_sdk():
-        return False
-    
-    print("\n=== Building for RP2040 ===\n")
-    
-    # Generate toolchain file
-    generate_pico_toolchain()
-    
-    # Generate CMakeLists.txt
-    if not generate_pico_cmake():
-        return False
-    
-    # Create build directory
-    mkdir(PICO_BUILD_DIR)
-    
-    # Run CMake with explicit toolchain
-    cmake_cmd = [
-        "cmake",
-        "-B", str(PICO_BUILD_DIR),
-        "-S", ".",
-        f"-DCMAKE_TOOLCHAIN_FILE={PICO_TOOLCHAIN_PATH}"
-    ]
-    run(cmake_cmd)
-    
-    # Build
-    build_cmd = ["cmake", "--build", str(PICO_BUILD_DIR), "-j4"]
-    run(build_cmd)
-    
-    # Show output files
-    uf2_file = PICO_BUILD_DIR / "sls.uf2"
-    if uf2_file.exists():
-        print(f"\nBuild successful! UF2 file: {uf2_file}")
-        print("To flash: Copy this file to your Pico in BOOTSEL mode")
-    
-    return True
-
-
-# ---------------------------------------------------------------------
-# MACOS BUILD
-# ---------------------------------------------------------------------
-def build_macos():
-    """Build for macOS (can be run on macOS or cross-compile on Linux)"""
-    print("\n=== Building for macOS ===\n")
-    
-    if PLATFORM != "macos" and PLATFORM != "linux":
-        print("ERROR: macOS builds require macOS or Linux with osxcross")
-        return False
-    
-    sources = list(SRC_DIR.glob("*.c"))
-    objects = [compile_source(s, is_test=False, target_platform="macos") for s in sources]
-    
-    macos_target = BIN_DIR / "sls_macos"
-    link_executable(objects, macos_target, target_platform="macos")
-    
-    print(f"\nBuild successful! Binary: {macos_target}")
-    return True
-
-
-# ---------------------------------------------------------------------
-# TARGETS
-# ---------------------------------------------------------------------
-def build_main():
-    sources = list(SRC_DIR.glob("*.c"))
-    objects = [compile_source(s, is_test=False) for s in sources]
-    link_executable(objects, TARGET)
-
-
-def build_tests():
-    generate_tests()
-    test_sources = list(TEST_DIR.glob("*.c"))
-    main_sources = [s for s in SRC_DIR.glob("*.c") if s.name != "main.c"]
-
-    test_objects = [compile_source(s, is_test=True) for s in test_sources]
-    shared_objects = [compile_source(s, is_test=False) for s in main_sources]
-
-    link_executable(test_objects + shared_objects, TEST_TARGET)
-
-
-def clean():
-    shutil.rmtree(OBJ_DIR, ignore_errors=True)
-    shutil.rmtree(BIN_DIR, ignore_errors=True)
-    shutil.rmtree(PICO_BUILD_DIR, ignore_errors=True)
-    cmake_file = Path("CMakeLists.txt")
-    if cmake_file.exists():
-        cmake_file.unlink()
-    toolchain_file = PICO_TOOLCHAIN_PATH
-    if toolchain_file.exists():
-        toolchain_file.unlink()
-    print("Cleaned.")
-
-
-def run_main():
-    build_main()
-    print("\n--- Running program ---\n")
-    subprocess.call([str(TARGET)])
-
-
-def run_tests():
-    build_tests()
-    print("\n--- Running tests ---\n")
-    subprocess.call([str(TEST_TARGET)])
-
-
-def debug_tests():
-    build_tests()
-    if os.name == "nt":
-        print("Debugging on Windows requires Visual Studio debugger.")
-    else:
-        subprocess.call(["gdb", str(TEST_TARGET)])
-
-
-def show_help():
-    help_text = """
-Build Script for Multi-Platform Compilation
-============================================
-
-Usage: python3 build.py [command]
-
-Commands:
-  all, main, build    Build for current platform
-  run                 Build and run program
-  test                Build and run tests
-  debug               Build tests and run debugger
-  clean               Remove build artifacts
-  
-  macos               Build for macOS
-  pico, rp2040        Build for RP2040 (Raspberry Pi Pico)
-  
-  help                Show this help message
-
-Environment Variables:
-  PICO_SDK_PATH       Path to Pico SDK (default: ~/pico/pico-sdk)
-
-Examples:
-  python3 build.py build      # Build for current platform
-  python3 build.py pico       # Build for RP2040
-  python3 build.py macos      # Build for macOS
-  python3 build.py clean      # Clean all build files
-"""
-    print(help_text)
-
-
-# ---------------------------------------------------------------------
-# ENTRY POINT
-# ---------------------------------------------------------------------
-def main():
-    if len(sys.argv) < 2:
-        show_help()
-        return
-
-    cmd = sys.argv[1]
-
-    match cmd:
-        case "all" | "main" | "build":
-            build_main()
-        case "run":
-            run_main()
-        case "test":
-            run_tests()
-        case "debug":
-            debug_tests()
-        case "clean":
-            clean()
-        case "macos":
-            build_macos()
-        case "pico" | "rp2040":
-            build_rp2040()
-        case "help" | "-h" | "--help":
-            show_help()
-        case _:
-            print(f"Unknown target: {cmd}")
-            print("Run 'python3 build.py help' for usage information")
-
-
-if __name__ == "__main__":
-    main()
diff --git a/SLS_C/sls_build/__init__.py b/SLS_C/sls_build/__init__.py
new file mode 100644
index 0000000..734c387
--- /dev/null
+++ b/SLS_C/sls_build/__init__.py
@@ -0,0 +1,5 @@
+# build/__init__.py
+__all__ = [
+"config",
+"utils",
+]
diff --git a/SLS_C/sls_build/__main__.py b/SLS_C/sls_build/__main__.py
new file mode 100644
index 0000000..a59b396
--- /dev/null
+++ b/SLS_C/sls_build/__main__.py
@@ -0,0 +1,4 @@
+
+if __name__ == "__main__":
+    from .cli import main
+    main()
diff --git a/SLS_C/sls_build/build_targets/base.py b/SLS_C/sls_build/build_targets/base.py
new file mode 100644
index 0000000..ec1076e
--- /dev/null
+++ b/SLS_C/sls_build/build_targets/base.py
@@ -0,0 +1,21 @@
+# build/build_targets/base.py
+from abc import ABC, abstractmethod
+from pathlib import Path
+from ..utils import mkdir
+
+class BuildTarget(ABC):
+    def __init__(self, platform, config, utils):
+        self.platform = platform
+        self.config = config
+        self.utils = utils
+
+    @abstractmethod
+    def sources(self) -> list[Path]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def output(self) -> Path:
+        raise NotImplementedError
+
+    def build(self):
+        raise NotImplementedError
diff --git a/SLS_C/sls_build/build_targets/main.py b/SLS_C/sls_build/build_targets/main.py
new file mode 100644
index 0000000..c17ee4a
--- /dev/null
+++ b/SLS_C/sls_build/build_targets/main.py
@@ -0,0 +1,25 @@
+# build/build_targets/main.py
+from .base import BuildTarget
+from pathlib import Path
+from ..utils import mkdir
+
+class MainBuild(BuildTarget):
+    def sources(self):
+        return [s for s in self.config.SRC_DIR.glob("*.c") if s.name not in ["pico_main.c"]]
+
+    def output(self):
+        return self.config.TARGET
+
+    def build(self):
+        mkdir(self.config.OBJ_DIR)
+        compiler = self.platform.compiler()
+        objects = []
+        for s in self.sources():
+            obj = self.config.OBJ_DIR / (s.stem + ".o")
+            deps = self.config.OBJ_DIR / (s.stem + ".d")
+            flags = self.platform.cflags(test=False)
+            extra = [f'-DGIT_COMMIT_HASH="{self.utils.git_commit_hash()}"']
+            compiler.compile(s, obj, flags, extra_defines=extra, deps_out=deps)
+            objects.append(obj)
+        mkdir(self.config.BIN_DIR)
+        compiler.link(objects, self.output(), libs=["-lm"])
diff --git a/SLS_C/sls_build/build_targets/rp2040.py b/SLS_C/sls_build/build_targets/rp2040.py
new file mode 100644
index 0000000..5dade64
--- /dev/null
+++ b/SLS_C/sls_build/build_targets/rp2040.py
@@ -0,0 +1,38 @@
+# build/build_targets/rp2040.py
+from .base import BuildTarget
+from ..config import RP2040_CMAKE_TEMPLATE, PICO_TOOLCHAIN_TEMPLATE
+from pathlib import Path
+from ..utils import run, mkdir
+
+class RP2040Build(BuildTarget):
+
+    def sources(self) -> list[Path]:
+        sources = list(self.config.SRC_DIR.glob("*.c"))
+        sources = [s for s in sources if s.name not in ["main.c", "repl.c", "file.c"] and "test" not in s.stem.lower()]
+        return sources
+
+    def prepare(self, project_name: str = "sls"):
+        # write toolchain
+        with open(self.config.PICO_TOOLCHAIN_PATH, "w") as f:
+            f.write(self.config.PICO_TOOLCHAIN_TEMPLATE)
+
+        # gather sources
+        sources = self.sources()
+        source_files = "\n".join(f"    {s}" for s in sources)
+        cmake_content = self.config.RP2040_CMAKE_TEMPLATE.format(
+            project_name=project_name,
+            source_files=source_files,
+            git_hash=self.utils.git_commit_hash(),
+            pico_sdk_path=str(self.config.PICO_SDK_PATH)
+        )
+        with open("CMakeLists.txt", "w") as f:
+            f.write(cmake_content)
+
+    def build(self):
+        if not self.platform.supports_rp2040():
+            raise RuntimeError("RP2040 build requirements not met")
+        print('\n=== Building for RP2040 ===\n')
+        self.prepare()
+        mkdir(self.config.PICO_BUILD_DIR)
+        run(["cmake", "-B", str(self.config.PICO_BUILD_DIR), "-S", ".", f"-DCMAKE_TOOLCHAIN_FILE={self.config.PICO_TOOLCHAIN_PATH}"])
+        run(["cmake", "--build", str(self.config.PICO_BUILD_DIR), "-j4"])
diff --git a/SLS_C/sls_build/build_targets/tests.py b/SLS_C/sls_build/build_targets/tests.py
new file mode 100644
index 0000000..ffeb81e
--- /dev/null
+++ b/SLS_C/sls_build/build_targets/tests.py
@@ -0,0 +1,27 @@
+# build/build_targets/tests.py
+from .base import BuildTarget
+from ..utils import mkdir
+
+class TestBuild(BuildTarget):
+    def sources(self):
+        tests = list(self.config.TEST_DIR.glob("*.c"))
+        main_sources = [s for s in self.config.SRC_DIR.glob("*.c") if s.name not in ["main.c", "pico_main.c"]]
+        return tests + main_sources
+
+    def output(self):
+        return self.config.TEST_TARGET
+
+    def build(self):
+        self.utils.mkdir(self.config.OBJ_DIR)
+        compiler = self.platform.compiler()
+        objects = []
+        for s in self.sources():
+            obj = self.config.OBJ_DIR / (s.stem + ".o")
+            deps = self.config.OBJ_DIR / (s.stem + ".d")
+            is_test = s.parent == self.config.TEST_DIR
+            flags = self.platform.cflags(test=is_test)
+            extra = [f'-DGIT_COMMIT_HASH="{self.utils.git_commit_hash()}"']
+            compiler.compile(s, obj, flags, extra_defines=extra, deps_out=deps)
+            objects.append(obj)
+        self.utils.mkdir(self.config.BIN_DIR)
+        compiler.link(objects, self.output(), libs=["-lm"])
diff --git a/SLS_C/sls_build/builder.py b/SLS_C/sls_build/builder.py
new file mode 100644
index 0000000..ac9c0d6
--- /dev/null
+++ b/SLS_C/sls_build/builder.py
@@ -0,0 +1,37 @@
+# build/builder.py
+from .platform import linux as linux_mod, macos as macos_mod, windows as windows_mod, rp2040 as rp_mod
+from .build_targets.main import MainBuild
+from .build_targets.tests import TestBuild
+from .build_targets.rp2040 import RP2040Build
+from . import config, utils
+
+PLATFORM_MAP = {
+    "linux": linux_mod.LinuxPlatform,
+    "macos": macos_mod.MacOSPlatform,
+    "windows": windows_mod.WindowsPlatform,
+    "rp2040": rp_mod.RP2040Platform,
+}
+
+
+def get_platform(name: str | None = None):
+    name = name or utils.detect_platform_name()
+    cls = PLATFORM_MAP.get(name, linux_mod.LinuxPlatform)
+    return cls()
+
+
+def build_main(platform_name: str | None = None):
+    plat = get_platform(platform_name)
+    target = MainBuild(plat, config, utils)
+    target.build()
+
+
+def build_tests(platform_name: str | None = None):
+    plat = get_platform(platform_name)
+    target = TestBuild(plat, config, utils)
+    target.build()
+
+
+def build_rp2040(platform_name: str | None = None):
+    plat = get_platform(platform_name or "rp2040")
+    target = RP2040Build(plat, config, utils)
+    target.build()
diff --git a/SLS_C/sls_build/cli.py b/SLS_C/sls_build/cli.py
new file mode 100644
index 0000000..199889c
--- /dev/null
+++ b/SLS_C/sls_build/cli.py
@@ -0,0 +1,33 @@
+# build/cli.py
+import sys
+from .builder import build_main, build_tests, build_rp2040
+from .utils import detect_platform_name
+
+
+def show_help():
+    print("Usage: python -m build.cli <command>")
+    print("Commands: build, run (not implemented), test, debug (not implemented), clean (not implemented), macos, pico")
+
+
+def main():
+    if len(sys.argv) < 2:
+        show_help()
+        return
+    cmd = sys.argv[1]
+    match cmd:
+        case "build" | "main":
+            build_main()
+        case "test":
+            build_tests()
+        case "pico" | "rp2040":
+            build_rp2040()
+        case "macos":
+            build_main("macos")
+        case "help" | "-h" | "--help":
+            show_help()
+        case _:
+            print(f"Unknown command: {cmd}")
+
+
+if __name__ == '__main__':
+    main()
diff --git a/SLS_C/sls_build/compiler/base.py b/SLS_C/sls_build/compiler/base.py
new file mode 100644
index 0000000..ff854b9
--- /dev/null
+++ b/SLS_C/sls_build/compiler/base.py
@@ -0,0 +1,18 @@
+# build/compiler/base.py
+from abc import ABC, abstractmethod
+from pathlib import Path
+
+class Compiler(ABC):
+    exe = None
+
+    def __init__(self, exe: str | None = None):
+        if exe:
+            self.exe = exe
+
+    @abstractmethod
+    def compile(self, src: Path, out: Path, flags: list[str], extra_defines: list[str] | None = None, deps_out: Path | None = None) -> Path:
+        ...
+
+    @abstractmethod
+    def link(self, objects: list[Path], output: Path, libs: list[str] | None = None):
+        ...
diff --git a/SLS_C/sls_build/compiler/clang.py b/SLS_C/sls_build/compiler/clang.py
new file mode 100644
index 0000000..fba30d3
--- /dev/null
+++ b/SLS_C/sls_build/compiler/clang.py
@@ -0,0 +1,6 @@
+# build/compiler/clang.py
+from .gcc import GCCCompiler
+
+class ClangCompiler(GCCCompiler):
+    def __init__(self, exe: str | None = None):
+        super().__init__(exe or "clang")
diff --git a/SLS_C/sls_build/compiler/gcc.py b/SLS_C/sls_build/compiler/gcc.py
new file mode 100644
index 0000000..2861803
--- /dev/null
+++ b/SLS_C/sls_build/compiler/gcc.py
@@ -0,0 +1,25 @@
+# build/compiler/gcc.py
+from .base import Compiler
+from pathlib import Path
+from ..utils import run
+
+class GCCCompiler(Compiler):
+    def __init__(self, exe: str | None = None):
+        super().__init__(exe or "gcc")
+
+    def compile(self, src: Path, out: Path, flags: list[str], extra_defines: list[str] | None = None, deps_out: Path | None = None) -> Path:
+        cmd = [self.exe] + flags[:]
+        if extra_defines:
+            cmd += extra_defines
+        if deps_out:
+            cmd += ["-MMD", "-MP"]
+        cmd += ["-c", str(src), "-o", str(out)]
+        run(cmd)
+        return out
+
+    def link(self, objects: list[Path], output: Path, libs: list[str] | None = None):
+        cmd = [self.exe] + [str(p) for p in objects]
+        if libs:
+            cmd += libs
+        cmd += ["-o", str(output)]
+        run(cmd)
diff --git a/SLS_C/sls_build/compiler/msvc.py b/SLS_C/sls_build/compiler/msvc.py
new file mode 100644
index 0000000..1d9a259
--- /dev/null
+++ b/SLS_C/sls_build/compiler/msvc.py
@@ -0,0 +1,21 @@
+# build/compiler/msvc.py
+from .base import Compiler
+from pathlib import Path
+from ..utils import run
+
+class MSVCCompiler(Compiler):
+    def __init__(self, exe: str | None = None):
+        super().__init__(exe or "cl")
+
+    def compile(self, src: Path, out: Path, flags: list[str], extra_defines: list[str] | None = None, deps_out: Path | None = None) -> Path:
+        # MSVC outputs object with /Fo
+        cmd = [self.exe] + flags[:]
+        if extra_defines:
+            cmd += extra_defines
+        cmd += ["/c", str(src), "/Fo" + str(out)]
+        run(cmd)
+        return out
+
+    def link(self, objects: list[Path], output: Path, libs: list[str] | None = None):
+        cmd = [self.exe] + [str(p) for p in objects] + ["/Fe" + str(output)]
+        run(cmd)
diff --git a/SLS_C/sls_build/config.py b/SLS_C/sls_build/config.py
new file mode 100644
index 0000000..0ba2eb9
--- /dev/null
+++ b/SLS_C/sls_build/config.py
@@ -0,0 +1,101 @@
+# build/config.py
+from pathlib import Path
+import os
+
+
+SRC_DIR = Path("src")
+TEST_DIR = Path("tests")
+OBJ_DIR = Path("obj")
+BIN_DIR = Path("bin")
+
+
+TARGET = BIN_DIR / "sls"
+TEST_TARGET = BIN_DIR / "sls_tests"
+
+
+PICO_SDK_PATH = Path(os.environ.get("PICO_SDK_PATH", Path.home() / "pico/pico-sdk"))
+PICO_BUILD_DIR = Path("build_pico")
+PICO_TOOLCHAIN_PATH = Path("pico_arm_gcc_toolchain.cmake")
+
+
+COMMON_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Werror", "-Iinclude", "-g"]
+TEST_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Wno-unused-function", "-Werror", "-Iinclude", "-g", "-O0"]
+MACOS_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Werror", "-Iinclude", "-g", "-mmacosx-version-min=10.13"]
+MSVC_FLAGS = ["/std:c11", "/Zi", "/Iinclude"]
+MSVC_TEST_FLAGS = MSVC_FLAGS + []
+
+
+PICO_TOOLCHAIN_TEMPLATE = """set(CMAKE_SYSTEM_NAME Generic)
+set(CMAKE_SYSTEM_PROCESSOR cortex-m0plus)
+
+
+set(CMAKE_C_COMPILER arm-none-eabi-gcc)
+set(CMAKE_CXX_COMPILER arm-none-eabi-g++)
+set(CMAKE_ASM_COMPILER arm-none-eabi-gcc)
+
+
+set(CMAKE_C_FLAGS_INIT "-mcpu=cortex-m0plus -mthumb")
+set(CMAKE_CXX_FLAGS_INIT "-mcpu=cortex-m0plus -mthumb")
+set(CMAKE_ASM_FLAGS_INIT "-mcpu=cortex-m0plus -mthumb")
+
+
+set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
+
+
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)
+"""
+
+
+RP2040_CMAKE_TEMPLATE = """cmake_minimum_required(VERSION 3.13)
+
+
+set(PICO_SDK_PATH "{pico_sdk_path}")
+include({pico_sdk_path}/external/pico_sdk_import.cmake)
+
+
+project({project_name} C CXX ASM)
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_CXX_STANDARD 17)
+
+
+pico_sdk_init()
+
+
+add_executable({project_name}
+{source_files}
+)
+
+
+set_target_properties({project_name} PROPERTIES
+OUTPUT_NAME "{project_name}.elf"
+SUFFIX ""
+)
+
+
+target_include_directories({project_name} PRIVATE
+${{CMAKE_CURRENT_LIST_DIR}}/include
+)
+
+
+target_compile_definitions({project_name} PRIVATE
+PICO_BUILD=1
+GIT_COMMIT_HASH="{git_hash}"
+)
+
+
+target_link_libraries({project_name}
+pico_stdlib
+hardware_uart
+hardware_gpio
+)
+
+
+pico_enable_stdio_usb({project_name} 1)
+pico_enable_stdio_uart({project_name} 1)
+
+
+pico_add_extra_outputs({project_name})
+"""
diff --git a/SLS_C/sls_build/platform/base.py b/SLS_C/sls_build/platform/base.py
new file mode 100644
index 0000000..e8f72f8
--- /dev/null
+++ b/SLS_C/sls_build/platform/base.py
@@ -0,0 +1,17 @@
+# build/platform/base.py
+from abc import ABC, abstractmethod
+from ..compiler.base import Compiler
+
+class Platform(ABC):
+    name = "generic"
+
+    @abstractmethod
+    def compiler(self) -> Compiler:
+        raise NotImplementedError
+
+    @abstractmethod
+    def cflags(self, test: bool = False):
+        return []
+
+    def supports_rp2040(self) -> bool:
+        return False
diff --git a/SLS_C/sls_build/platform/linux.py b/SLS_C/sls_build/platform/linux.py
new file mode 100644
index 0000000..2e414c6
--- /dev/null
+++ b/SLS_C/sls_build/platform/linux.py
@@ -0,0 +1,13 @@
+# build/platform/linux.py
+from .base import Platform
+from ..compiler.gcc import GCCCompiler
+from ..config import COMMON_FLAGS, TEST_FLAGS
+
+class LinuxPlatform(Platform):
+    name = "linux"
+
+    def compiler(self):
+        return GCCCompiler()
+
+    def cflags(self, test: bool = False):
+        return TEST_FLAGS if test else COMMON_FLAGS
diff --git a/SLS_C/sls_build/platform/macos.py b/SLS_C/sls_build/platform/macos.py
new file mode 100644
index 0000000..9b6be14
--- /dev/null
+++ b/SLS_C/sls_build/platform/macos.py
@@ -0,0 +1,13 @@
+# build/platform/macos.py
+from .base import Platform
+from ..compiler.clang import ClangCompiler
+from ..config import MACOS_FLAGS, TEST_FLAGS
+
+class MacOSPlatform(Platform):
+    name = "macos"
+
+    def compiler(self):
+        return ClangCompiler()
+
+    def cflags(self, test: bool = False):
+        return (TEST_FLAGS + ["-mmacosx-version-min=10.13"]) if test else MACOS_FLAGS
diff --git a/SLS_C/sls_build/platform/rp2040.py b/SLS_C/sls_build/platform/rp2040.py
new file mode 100644
index 0000000..13597ed
--- /dev/null
+++ b/SLS_C/sls_build/platform/rp2040.py
@@ -0,0 +1,19 @@
+# build/platform/rp2040.py
+from .base import Platform
+from ..compiler.gcc import GCCCompiler
+from ..config import COMMON_FLAGS, TEST_FLAGS, PICO_SDK_PATH
+from pathlib import Path
+import shutil
+
+class RP2040Platform(Platform):
+    name = "rp2040"
+
+    def compiler(self):
+        return GCCCompiler("arm-none-eabi-gcc")
+
+    def cflags(self, test: bool = False):
+        return TEST_FLAGS if test else COMMON_FLAGS
+
+    def supports_rp2040(self) -> bool:
+        sdk = Path(PICO_SDK_PATH)
+        return sdk.exists() and shutil.which("arm-none-eabi-gcc") is not None
diff --git a/SLS_C/sls_build/platform/windows.py b/SLS_C/sls_build/platform/windows.py
new file mode 100644
index 0000000..7d9f33a
--- /dev/null
+++ b/SLS_C/sls_build/platform/windows.py
@@ -0,0 +1,13 @@
+# build/platform/windows.py
+from .base import Platform
+from ..compiler.msvc import MSVCCompiler
+from ..config import MSVC_FLAGS, MSVC_TEST_FLAGS
+
+class WindowsPlatform(Platform):
+    name = "windows"
+
+    def compiler(self):
+        return MSVCCompiler()
+
+    def cflags(self, test: bool = False):
+        return MSVC_TEST_FLAGS if test else MSVC_FLAGS
diff --git a/SLS_C/sls_build/utils.py b/SLS_C/sls_build/utils.py
new file mode 100644
index 0000000..093eb8f
--- /dev/null
+++ b/SLS_C/sls_build/utils.py
@@ -0,0 +1,49 @@
+# build/utils.py
+from pathlib import Path
+import subprocess
+import os
+import shutil
+
+
+def mkdir(p: Path):
+    p.mkdir(parents=True, exist_ok=True)
+
+
+def run(cmd, **kwargs):
+    print(">>", " ".join(str(c) for c in cmd))
+    subprocess.check_call(cmd, **kwargs)
+
+
+def detect_platform_name():
+    import platform
+    system = platform.system()
+    if system == "Darwin":
+        return "macos"
+    if system == "Windows":
+        return "windows"
+    if system == "Linux":
+        return "linux"
+    return "unknown"
+
+
+def git_commit_hash():
+    try:
+        result_hash = subprocess.check_output([
+            "git", "describe", "--always", "--dirty", "--abbrev=7"
+        ], text=True, stderr=subprocess.DEVNULL).strip()
+        result_date = subprocess.check_output([
+            "git", "show", "-s", "--format=%ci"
+        ], text=True, stderr=subprocess.DEVNULL).strip()
+        return f"{result_hash} {result_date}"
+    except Exception:
+        return "unknown"
+
+
+def is_up_to_date(src: Path, obj: Path, dep: Path):
+    if "meta" in [src.stem, obj.stem, dep.stem]:
+        return False
+    if not obj.exists():
+        return False
+    if dep.exists() and dep.stat().st_mtime > obj.stat().st_mtime:
+        return False
+    return src.stat().st_mtime < obj.stat().st_mtime