diff --git a/src/plasma_simulation/__init__.py b/src/plasma_simulation/__init__.py
new file mode 100644
index 0000000..640b291
--- /dev/null
+++ b/src/plasma_simulation/__init__.py
@@ -0,0 +1,5 @@
+from plasma_simulation.base import SimulationBase
+
+__all__ = [
+    "SimulationBase",
+]
diff --git a/src/plasma_simulation/base.py b/src/plasma_simulation/base.py
new file mode 100644
index 0000000..8fcc85b
--- /dev/null
+++ b/src/plasma_simulation/base.py
@@ -0,0 +1,60 @@
+from abc import ABCMeta, abstractmethod
+
+
+class SimulationBase(metaclass=ABCMeta):
+    """Abstract base class for simulations."""
+
+    @abstractmethod
+    def __init__(self, **kwargs):
+        """Initialize the simulation."""
+        pass
+
+    @abstractmethod
+    def allocate(self, verbose: bool = False):
+        """Allocate the simulation variables in memory."""
+        pass
+
+    @abstractmethod
+    def save_geometry_and_equil_vtk(self, verbose: bool = False):
+        """Save geometry and equilibrium in VTK format."""
+        pass
+
+    @abstractmethod
+    def initialize_data_storage(self, verbose: bool = False):
+        """Initialize the simulation data storage."""
+        pass
+
+    @abstractmethod
+    def run(self, verbose: bool = False):
+        """Run the simulation."""
+        pass
+
+    @abstractmethod
+    def pproc(self, verbose: bool = False):
+        """Post-process the simulation results."""
+        pass
+
+    @abstractmethod
+    def load_plotting_data(self, verbose: bool = False):
+        """Load post-processed data for visualization."""
+        pass
+
+    @abstractmethod
+    def to_dict(self) -> dict:
+        """Serialize the simulation configuration to a dictionary."""
+        pass
+
+    @abstractmethod
+    def from_dict(cls, dct: dict):
+        """Deserialize a simulation configuration from a dictionary."""
+        pass
+
+    @abstractmethod
+    def from_file(cls, file_path: str):
+        """Deserialize a simulation configuration from a file."""
+        pass
+
+    @abstractmethod
+    def export(self, file_path: str):
+        """Export a simulation configuration to a YAML or JSON file based on the file extension."""
+        pass
diff --git a/src/plasma_simulation/tests/test_app.py b/src/plasma_simulation/tests/test_app.py
new file mode 100644
index 0000000..300746b
--- /dev/null
+++ b/src/plasma_simulation/tests/test_app.py
@@ -0,0 +1,18 @@
+import pytest
+
+from plasma_simulation import SimulationBase
+
+
+def test_import_app():
+    # Import check and API surface check.
+    assert SimulationBase is not None
+
+
+def test_simulation_base_is_abstract():
+    with pytest.raises(TypeError, match="abstract class SimulationBase"):
+        SimulationBase()
+
+
+if __name__ == "__main__":
+    test_import_app()
+    test_simulation_base_is_abstract()
diff --git a/src/plasma_simulation/tests/unit/__init__.py b/src/plasma_simulation/tests/unit/__init__.py
deleted file mode 100644
index e69de29..0000000
diff --git a/src/plasma_simulation/tests/unit/test_app.py b/src/plasma_simulation/tests/unit/test_app.py
deleted file mode 100644
index 04c3681..0000000
--- a/src/plasma_simulation/tests/unit/test_app.py
+++ /dev/null
@@ -1,9 +0,0 @@
-def test_import_app():
-    from plasma_simulation.main import main
-
-    print("app imported")
-    main()
-
-
-if __name__ == "__main__":
-    test_import_app()