diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..3b41e12
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,126 @@
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..c8e3a2f
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,39 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v4.6.0
+  hooks:
+  - id: trailing-whitespace
+  - id: end-of-file-fixer
+  - id: check-shebang-scripts-are-executable
+  - id: check-toml
+  - id: check-yaml
+  - id: check-added-large-files
+  - id: debug-statements
+    language_version: python3
+
+- repo: https://github.com/astral-sh/ruff-pre-commit
+  # Ruff version.
+  rev: v0.5.7
+  hooks:
+  # Run the linter.
+  - id: ruff
+    types_or: [ python, pyi, jupyter ]
+    args: [ --fix ]
+  # Run the formatter.
+  - id: ruff-format
+    types_or: [ python, pyi, jupyter ]
+
+- repo: https://github.com/asottile/pyupgrade
+  rev: v3.17.0
+  hooks:
+  - id: pyupgrade
+
+- repo: https://github.com/pre-commit/mirrors-mypy
+  rev: v1.11.1
+  hooks:
+  - id: mypy
+
+default_language_version:
+    python: python3.12
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..a4ca234
--- /dev/null
+++ b/README.md
@@ -0,0 +1 @@
+## MindLess Molecule GENerator
diff --git a/environment.yml b/environment.yml
new file mode 100644
index 0000000..4e1db69
--- /dev/null
+++ b/environment.yml
@@ -0,0 +1,13 @@
+# conda env create -f environment.yaml
+name: mlmgen
+channels:
+  - conda-forge
+dependencies:
+  - ruff
+  - coverage
+  - numpy
+  - pre-commit
+  - pytest
+  - tox
+  - pip:
+      - covdefaults
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..499b707
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,54 @@
+[build-system]
+requires = ["wheel", "setuptools>=64", "setuptools_scm>=8"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "mlmgen"
+authors = [
+    { name = "Marcel Müller", email = "marcel.mueller@thch.uni-bonn.de" },
+]
+description = "MindLess Molecule GENerator"
+readme = "README.md"
+requires-python = ">=3.8"
+license = { file = "LICENSE.md" }
+classifiers = [
+    "License :: OSI Approved :: MIT License",
+    "Programming Language :: Python :: 3 :: Only",
+    "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Topic :: Scientific/Engineering",
+    "Typing :: Typed",
+]
+dependencies = ["numpy"]
+dynamic = ["version"]
+
+[project.optional-dependencies]
+dev = [
+    "ruff",
+    "covdefaults",
+    "coverage",
+    "pre-commit",
+    "pytest",
+    "tox",
+    "setuptools_scm>=8",
+]
+
+[project.scripts]
+mlmgen = "mlmgen:console_entry_point"
+
+[tool.setuptools_scm]
+version_file = "src/mlmgen/__version__.py"
+
+[tool.pytest.ini_options]
+testpaths = ["test"]
+pythonpath = ["src"]
+
+[tool.coverage.run]
+plugins = ["covdefaults"]
+source = ["./src"]
+
+[tool.coverage.report]
+fail_under = 50
diff --git a/src/mlmgen/__init__.py b/src/mlmgen/__init__.py
new file mode 100644
index 0000000..a1e18cd
--- /dev/null
+++ b/src/mlmgen/__init__.py
@@ -0,0 +1,12 @@
+"""
+Squarer
+=======
+
+Dummy command line tool to square a number.
+"""
+
+from .__version__ import __version__
+from .cli import console_entry_point
+from .mymath import square_a_number as square
+
+__all__ = ["__version__", "console_entry_point", "square"]
diff --git a/src/mlmgen/__main__.py b/src/mlmgen/__main__.py
new file mode 100644
index 0000000..3a0878f
--- /dev/null
+++ b/src/mlmgen/__main__.py
@@ -0,0 +1,9 @@
+"""
+Entry point for command line interface via `python -m <prog>`.
+"""
+
+from .cli import console_entry_point
+
+if __name__ == "__main__":
+    # print("Hello from __main__.py")
+    raise SystemExit(console_entry_point())
diff --git a/src/mlmgen/__version__.py b/src/mlmgen/__version__.py
new file mode 100644
index 0000000..c134c07
--- /dev/null
+++ b/src/mlmgen/__version__.py
@@ -0,0 +1,17 @@
+# file generated by setuptools_scm
+# don't change, don't track in version control
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from typing import Tuple, Union
+
+    VERSION_TUPLE = Tuple[Union[int, str], ...]
+else:
+    VERSION_TUPLE = object
+
+version: str
+__version__: str
+__version_tuple__: VERSION_TUPLE
+version_tuple: VERSION_TUPLE
+
+__version__ = version = "0.1.dev26+g7432299.d20240810"
+__version_tuple__ = version_tuple = (0, 1, "dev26", "g7432299.d20240810")
diff --git a/src/mlmgen/cli/__init__.py b/src/mlmgen/cli/__init__.py
new file mode 100644
index 0000000..50f7ccf
--- /dev/null
+++ b/src/mlmgen/cli/__init__.py
@@ -0,0 +1,10 @@
+"""
+Command line interface
+======================
+
+This module contains functionality for the CLI.
+"""
+
+from .entrypoint import console_entry_point
+
+__all__ = ["console_entry_point"]
diff --git a/src/mlmgen/cli/entrypoint.py b/src/mlmgen/cli/entrypoint.py
new file mode 100644
index 0000000..ba8c087
--- /dev/null
+++ b/src/mlmgen/cli/entrypoint.py
@@ -0,0 +1,22 @@
+"""
+Entrypoint for command line interface.
+"""
+
+from __future__ import annotations
+
+import argparse
+from collections.abc import Sequence
+
+from ..mymath import square_a_number as square
+
+
+def console_entry_point(argv: Sequence[str] | None = None) -> int:
+    # get command line argument
+    parser = argparse.ArgumentParser()
+    parser.add_argument("number", type=float, help="Number to square.")
+    args = parser.parse_args(argv)
+
+    # print result
+    print(square(args.number))
+
+    return 0
diff --git a/src/mlmgen/mymath/__init__.py b/src/mlmgen/mymath/__init__.py
new file mode 100644
index 0000000..a372fc0
--- /dev/null
+++ b/src/mlmgen/mymath/__init__.py
@@ -0,0 +1,10 @@
+"""
+Math
+====
+
+This module contains all mathematical functions.
+"""
+
+from .calc import square_a_number
+
+__all__ = ["square_a_number"]
diff --git a/src/mlmgen/mymath/calc.py b/src/mlmgen/mymath/calc.py
new file mode 100644
index 0000000..85cfb85
--- /dev/null
+++ b/src/mlmgen/mymath/calc.py
@@ -0,0 +1,12 @@
+"""
+Mathematical functions.
+"""
+
+from __future__ import annotations
+
+
+def square_a_number(a: float | int) -> float | int:
+    if not isinstance(a, (float, int)):
+        raise TypeError("Float or int expected.")
+
+    return a * a
diff --git a/test/__init__.py b/test/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/test/conftest.py b/test/conftest.py
new file mode 100644
index 0000000..3273d1f
--- /dev/null
+++ b/test/conftest.py
@@ -0,0 +1,10 @@
+"""
+Setup for pytest.
+"""
+
+import numpy as np
+
+# import pytest
+
+np.random.seed(0)
+np.set_printoptions(precision=16)
diff --git a/test/test_cli/__init__.py b/test/test_cli/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/test/test_cli/test_entrypoint.py b/test/test_cli/test_entrypoint.py
new file mode 100644
index 0000000..dd6ab2f
--- /dev/null
+++ b/test/test_cli/test_entrypoint.py
@@ -0,0 +1,16 @@
+"""
+Test program call from command line.
+"""
+
+import pytest
+
+from mlmgen.cli import console_entry_point
+
+
+def test_entrypoint(capsys: pytest.CaptureFixture) -> None:
+    # pylint: disable=too-many-function-args
+    console_entry_point(["2.0"])
+
+    out, err = capsys.readouterr()
+    assert out == "4.0\n"
+    assert err == ""
diff --git a/test/test_mymath/__init__.py b/test/test_mymath/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/test/test_mymath/test_square.py b/test/test_mymath/test_square.py
new file mode 100644
index 0000000..4913e8d
--- /dev/null
+++ b/test/test_mymath/test_square.py
@@ -0,0 +1,28 @@
+"""
+Test the squaring function.
+"""
+
+from __future__ import annotations
+
+import numpy as np
+import pytest
+
+from mlmgen.mymath import square_a_number
+
+
+@pytest.mark.parametrize("value", [1.0, 2, -3.0])
+def test_squarer(value: int | float) -> None:
+    expected = value * value
+    actual = square_a_number(value)
+
+    assert pytest.approx(expected) == actual
+
+
+def test_squarer_fail() -> None:
+    with pytest.raises(TypeError):
+        square_a_number("2")  # type: ignore
+
+
+def test_dummy() -> None:
+    # show effect of `conftest.py` by setting printoptions
+    print(np.array([1.0 / 3.0]))
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..a5f4db0
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,13 @@
+[tox]
+envlist = py{312}
+
+[testenv]
+deps =
+    covdefaults
+    coverage
+    pytest
+commands =
+    coverage erase
+    coverage run -m pytest -svv {posargs:test}
+    coverage report -m
+    coverage xml -o coverage.xml