diff --git a/.gitignore b/.gitignore
index a807f4e..f3709c0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 src/__pycache__/
+_build/
 NewLang
diff --git a/Makefile b/Makefile
index 21f2ad1..c07c906 100644
--- a/Makefile
+++ b/Makefile
@@ -1,8 +1,27 @@
+SHELL=/bin/bash
+
 build: clean_pycache
 	python3 -m zipapp src -p "/usr/bin/env python3" -c -m "main:main" -o NewLang
 
 clean_pycache:
 	test ! -d src/__pycache__ || rm -r src/__pycache__
 
-clean: clean_pycache
+clean: clean_pycache clean_build
 	test ! -e NewLang || rm NewLang
+
+_build:
+	mkdir -p _build
+
+_build/.stamp_venv: _build
+	python3 -m venv _build/venv
+	source _build/venv/bin/activate && pip install -r requirements.txt
+	touch _build/.stamp_venv
+
+tidy: _build/.stamp_venv
+	source _build/venv/bin/activate && black src
+
+clean_build:
+	rm -rf _build/
+
+venv_bash: _build/.stamp_venv
+	source _build/venv/bin/activate && bash
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..7e66a17
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+black