diff --git a/.github/workflows/run_tests.yml b/.github/workflows/run_tests.yml
index f597e14..85943b2 100644
--- a/.github/workflows/run_tests.yml
+++ b/.github/workflows/run_tests.yml
@@ -34,9 +34,11 @@ jobs:
       
       - name: Set up Python
         uses: actions/setup-python@v5
+        with:
+          python-version: '>=3.10'
 
       - name: Install dependencies
-        run: pip install -r requirements.txt
+        run: pip install . && pip uninstall -y project_template
 
       - name: Install test dependencies
         run: pip install pytest pytest-cov codecov
diff --git a/.vscode/launch.json b/.vscode/launch.json
index b73668d..6322f39 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -5,10 +5,10 @@
     "version": "0.2.0",
     "configurations": [
         {
-            "name": "Print version",
+            "name": "Use adder",
             "type": "debugpy",
             "request": "launch",
-            "program": "${workspaceFolder}/examples/print_version.py",
+            "program": "${workspaceFolder}/examples/use_adder.py",
             "console": "integratedTerminal",
             "justMyCode": true,
             "env": {"PYTHONPATH": "${workspaceFolder}"},
diff --git a/environment.yml b/environment.yml
deleted file mode 100644
index 4a72774..0000000
--- a/environment.yml
+++ /dev/null
@@ -1,6 +0,0 @@
-# create a dev conda environment with: `make create_env` or `conda env create -f environment.yml`
-name: project_template
-channels:
-- conda-forge
-dependencies:
-- numpy
diff --git a/examples/print_version.py b/examples/print_version.py
deleted file mode 100644
index 9a7f2e9..0000000
--- a/examples/print_version.py
+++ /dev/null
@@ -1,9 +0,0 @@
-import project_template
-
-
-def main():
-    print(project_template.__version__)
-
-
-if __name__ == "__main__":
-    main()
diff --git a/examples/use_adder.py b/examples/use_adder.py
new file mode 100644
index 0000000..6f8133a
--- /dev/null
+++ b/examples/use_adder.py
@@ -0,0 +1,16 @@
+import project_template
+import numpy as np
+
+
+def main():
+    a = np.array([1, 2, 3])
+    b = np.array([4, 5, 6])
+    result = project_template.adder(a, b)
+    print(
+        f"The result of adding {a} and {b} is {result}.\n"
+        f'This is computed using project_template.adder from version "{project_template.__version__}"'
+    )
+
+
+if __name__ == "__main__":
+    main()
diff --git a/project_template/__init__.py b/project_template/__init__.py
index 58f3ace..12053b2 100644
--- a/project_template/__init__.py
+++ b/project_template/__init__.py
@@ -1 +1,8 @@
 from .version import __version__
+
+from .adder import adder
+
+__all__ = [
+    "__version__",
+    adder.__name__,
+]
diff --git a/project_template/adder.py b/project_template/adder.py
new file mode 100644
index 0000000..9a42285
--- /dev/null
+++ b/project_template/adder.py
@@ -0,0 +1,5 @@
+import numpy as np
+
+
+def adder(a: np.array, b: np.array) -> np.array:
+    return a + b
diff --git a/pyproject.toml b/pyproject.toml
index 14d6e10..9287d4b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,8 @@
 [build-system]
-requires = ["setuptools", "setuptools-scm"]
+requires = [
+    "setuptools", 
+    "numpy",
+]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -15,6 +18,9 @@ classifiers = [
     "Programming Language :: Python"
 ]
 requires-python = ">=3.10"
+dependencies = [
+    "numpy", 
+]
 
 [project.optional-dependencies]
 test = ["pytest"]
diff --git a/requirements.txt b/requirements.txt
deleted file mode 100644
index 24ce15a..0000000
--- a/requirements.txt
+++ /dev/null
@@ -1 +0,0 @@
-numpy
diff --git a/setup.py b/setup.py
deleted file mode 100644
index 7e95563..0000000
--- a/setup.py
+++ /dev/null
@@ -1,9 +0,0 @@
-from setuptools import setup
-
-
-def read_requirements():
-    with open("requirements.txt") as f:
-        return f.read().splitlines()
-
-
-setup(install_requires=read_requirements())
diff --git a/tests/test_file.py b/tests/test_file.py
index 6443bf1..98f2efe 100644
--- a/tests/test_file.py
+++ b/tests/test_file.py
@@ -1,5 +1,13 @@
+import numpy as np
 import project_template
 
 
 def test_version():
     assert project_template.__version__ == "0.1.0"
+
+
+def test_adder():
+    a = np.array([1, 2, 3])
+    b = np.array([4, 5, 6])
+    result = project_template.adder(a, b)
+    assert np.all(result == np.array([5, 7, 9]))