diff --git a/control.example.yml b/control.example.yml
index 0830d4d..6ecbb53 100644
--- a/control.example.yml
+++ b/control.example.yml
@@ -1,7 +1,8 @@
 diceplayer:
-    opt: no
+    type: both
+    switch_cyc: 3
+    max_cyc: 5
     mem: 24
-    maxcyc: 5
     ncores: 5
     nprocs: 4
     qmprog: 'g16'
diff --git a/diceplayer/__main__.py b/diceplayer/__main__.py
index 762680f..fed4452 100644
--- a/diceplayer/__main__.py
+++ b/diceplayer/__main__.py
@@ -1,4 +1,5 @@
 from diceplayer.cli import ArgsModel, read_input
+from diceplayer.config import PlayerConfig
 from diceplayer.logger import logger
 from diceplayer.player import Player
 
@@ -33,13 +34,26 @@ def main():
         metavar="OUTFILE",
         help="output file of diceplayer [default = run.log]",
     )
+    parser.add_argument(
+        "-f",
+        "--force",
+        dest="force",
+        default=False,
+        action="store_true",
+        help="force overwrite existing state file if it exists [default = False]",
+    )
     args = ArgsModel.from_args(parser.parse_args())
 
     logger.set_output_file(args.outfile)
 
-    config = read_input(args.infile)
+    config: PlayerConfig
+    try:
+        config = read_input(args.infile)
+    except Exception as e:
+        logger.error(f"Failed to read input file: {e}")
+        return
 
-    Player(config).play(continuation=args.continuation)
+    Player(config).play(continuation=args.continuation, force=args.force)
 
 
 if __name__ == "__main__":
diff --git a/diceplayer/cli/args_model.py b/diceplayer/cli/args_model.py
index 8c5feaa..5cf107a 100644
--- a/diceplayer/cli/args_model.py
+++ b/diceplayer/cli/args_model.py
@@ -5,6 +5,7 @@ class ArgsModel(BaseModel):
     outfile: str
     infile: str
     continuation: bool
+    force: bool
 
     @classmethod
     def from_args(cls, args):
diff --git a/diceplayer/cli/read_input_file.py b/diceplayer/cli/read_input_file.py
index 36f8946..5fd6d82 100644
--- a/diceplayer/cli/read_input_file.py
+++ b/diceplayer/cli/read_input_file.py
@@ -1,13 +1,9 @@
 from diceplayer.config import PlayerConfig
-from diceplayer.logger import logger
 
 import yaml
 
 
 def read_input(infile) -> PlayerConfig:
-    try:
-        with open(infile, "r") as f:
-            return PlayerConfig.model_validate(yaml.safe_load(f))
-    except Exception as e:
-        logger.exception("Failed to read input file")
-        raise e
+    with open(infile, "r") as f:
+        values = yaml.safe_load(f)
+        return PlayerConfig.model_validate(values["diceplayer"])
diff --git a/diceplayer/config/dice_config.py b/diceplayer/config/dice_config.py
index ccfebd8..e788378 100644
--- a/diceplayer/config/dice_config.py
+++ b/diceplayer/config/dice_config.py
@@ -1,11 +1,12 @@
-from pydantic import BaseModel, Field, ConfigDict
-from typing_extensions import List, Literal
+from pydantic import BaseModel, ConfigDict, Field
+from typing_extensions import Literal
 
 
 class DiceConfig(BaseModel):
     """
     Data Transfer Object for the Dice configuration.
     """
+
     model_config = ConfigDict(
         frozen=True,
     )
@@ -15,10 +16,10 @@ class DiceConfig(BaseModel):
         ..., description="Name of the output file for the simulation results"
     )
     dens: float = Field(..., description="Density of the system")
-    nmol: List[int] = Field(
+    nmol: list[int] = Field(
         ..., description="List of the number of molecules for each component"
     )
-    nstep: List[int] = Field(
+    nstep: list[int] = Field(
         ...,
         description="List of the number of steps for each component",
         min_length=2,
diff --git a/diceplayer/config/gaussian_config.py b/diceplayer/config/gaussian_config.py
index ea2d5c2..3ea014e 100644
--- a/diceplayer/config/gaussian_config.py
+++ b/diceplayer/config/gaussian_config.py
@@ -1,4 +1,4 @@
-from pydantic import BaseModel, Field, ConfigDict
+from pydantic import BaseModel, ConfigDict, Field
 from typing_extensions import Literal
 
 
@@ -6,14 +6,15 @@ class GaussianConfig(BaseModel):
     """
     Data Transfer Object for the Gaussian configuration.
     """
+
     model_config = ConfigDict(
         frozen=True,
     )
 
-    level: str = Field(..., description="Level of theory for the QM calculations")
     qmprog: Literal["g03", "g09", "g16"] = Field(
         "g16", description="QM program to use for the calculations"
     )
+    level: str = Field(..., description="Level of theory for the QM calculations")
 
     chgmult: list[int] = Field(
         default_factory=lambda: [0, 1],
@@ -23,6 +24,6 @@ class GaussianConfig(BaseModel):
         "chelpg", description="Population analysis method for the QM calculations"
     )
     chg_tol: float = Field(0.01, description="Charge tolerance for the QM calculations")
-    keywords: str = Field(
+    keywords: str | None = Field(
         None, description="Additional keywords for the QM calculations"
     )
diff --git a/diceplayer/config/player_config.py b/diceplayer/config/player_config.py
index ab7caa3..82701ef 100644
--- a/diceplayer/config/player_config.py
+++ b/diceplayer/config/player_config.py
@@ -1,9 +1,10 @@
 from diceplayer.config.dice_config import DiceConfig
 from diceplayer.config.gaussian_config import GaussianConfig
 
-from pydantic import BaseModel, Field, model_validator, ConfigDict
-from typing_extensions import Self, Any
+from pydantic import BaseModel, ConfigDict, Field, model_validator
+from typing_extensions import Any
 
+from enum import Enum
 from pathlib import Path
 
 
@@ -11,18 +12,28 @@ MIN_STEP = 20000
 STEP_INCREMENT = 1000
 
 
+class RoutineType(str, Enum):
+    CHARGE = "charge"
+    GEOMETRY = "geometry"
+    BOTH = "both"
+
+
 class PlayerConfig(BaseModel):
     """
     Data Transfer Object for the player configuration.
     """
+
     model_config = ConfigDict(
         frozen=True,
     )
 
-    opt: bool = Field(..., description="Whether to perform geometry optimization")
-    maxcyc: int = Field(
-        ..., description="Maximum number of cycles for the geometry optimization"
+    type: RoutineType = Field(..., description="Type of simulation to perform")
+    max_cyc: int = Field(
+        ..., description="Maximum number of cycles for the geometry optimization", gt=0
     )
+    switch_cyc: int = Field(..., description="Switch cycle configuration")
+
+    mem: int = Field(None, description="Memory configuration")
     nprocs: int = Field(
         ..., description="Number of processors to use for the QM calculations"
     )
@@ -33,22 +44,37 @@ class PlayerConfig(BaseModel):
     dice: DiceConfig = Field(..., description="Dice configuration")
     gaussian: GaussianConfig = Field(..., description="Gaussian configuration")
 
-    mem: int = Field(None, description="Memory configuration")
-    switchcyc: int = Field(3, description="Switch cycle configuration")
-    qmprog: str = Field("g16", description="QM program to use for the calculations")
     altsteps: int = Field(
         20000, description="Number of steps for the alternate simulation"
     )
     geoms_file: Path = Field(
-        "geoms.xyz", description="File name for the geometries output"
+        Path("geoms.xyz"), description="File name for the geometries output"
     )
     simulation_dir: Path = Field(
-        "simfiles", description="Directory name for the simulation files"
+        Path("simfiles"), description="Directory name for the simulation files"
     )
 
     @model_validator(mode="before")
     @staticmethod
     def validate_altsteps(fields) -> dict[str, Any]:
         altsteps = fields.pop("altsteps", MIN_STEP)
-        fields["altsteps"] = round(max(MIN_STEP, altsteps) / STEP_INCREMENT) * STEP_INCREMENT
+        fields["altsteps"] = (
+            round(max(MIN_STEP, altsteps) / STEP_INCREMENT) * STEP_INCREMENT
+        )
+        return fields
+
+    @model_validator(mode="before")
+    @staticmethod
+    def validate_switch_cyc(fields: dict[str, Any]) -> dict[str, Any]:
+        max_cyc = int(fields.get("max_cyc", 0))
+        switch_cyc = int(fields.get("switch_cyc", max_cyc))
+
+        if fields.get("type") == "both" and not switch_cyc < max_cyc:
+            raise ValueError("switch_cyc must be less than max_cyc when type='both'.")
+
+        if fields.get("type") != "both" and switch_cyc != max_cyc:
+            raise ValueError(
+                "switch_cyc must be equal to max_cyc when type is not 'both'."
+            )
+
         return fields
diff --git a/diceplayer/player.py b/diceplayer/player.py
index 8aff1c7..54cb094 100644
--- a/diceplayer/player.py
+++ b/diceplayer/player.py
@@ -1,8 +1,41 @@
 from diceplayer.config.player_config import PlayerConfig
+from diceplayer.logger import logger
+from diceplayer.state.state_handler import StateHandler
+from diceplayer.state.state_model import StateModel
+
+from typing_extensions import TypedDict, Unpack
+
+
+class PlayerFlags(TypedDict):
+    continuation: bool
+    force: bool
 
 
 class Player:
     def __init__(self, config: PlayerConfig):
         self.config = config
 
-    def play(self, continuation=False): ...
+    def play(self, **flags: Unpack[PlayerFlags]):
+        state_handler = StateHandler(self.config.simulation_dir)
+
+        if not flags["continuation"]:
+            logger.info(
+                "Continuation flag is not set. Starting a new simulation and deleting any existing state."
+            )
+            state_handler.delete()
+
+        state = state_handler.get(self.config, force=flags["force"])
+
+        if state is None:
+            state = StateModel.from_config(self.config)
+        else:
+            logger.info("Resuming from existing state.")
+
+        while state.current_cycle < self.config.max_cyc:
+            logger.info(
+                f"Starting cycle {state.current_cycle + 1} of {self.config.max_cyc}."
+            )
+            state.current_cycle += 1
+            state_handler.save(state)
+
+        logger.info("Reached maximum number of cycles. Simulation complete.")
diff --git a/diceplayer/state/state_handler.py b/diceplayer/state/state_handler.py
index fa456f4..b2056f4 100644
--- a/diceplayer/state/state_handler.py
+++ b/diceplayer/state/state_handler.py
@@ -1,31 +1,37 @@
-import pickle
-from pathlib import Path
-
 from diceplayer.config import PlayerConfig
-from diceplayer.environment import System
 from diceplayer.logger import logger
 from diceplayer.state.state_model import StateModel
 
+import pickle
+from pathlib import Path
+
 
 class StateHandler:
     def __init__(self, sim_dir: Path, state_file: str = "state.pkl"):
+        if not sim_dir.exists():
+            sim_dir.mkdir(parents=True, exist_ok=True)
         self._state_file = sim_dir / state_file
 
-    def get_state(self, config: PlayerConfig) -> StateModel | None:
+    def get(self, config: PlayerConfig, force=False) -> StateModel | None:
         if not self._state_file.exists():
             return None
 
-        with self._state_file.open(mode="r") as f:
-            data = pickle.load(f)
-
+        with open(self._state_file, mode="rb") as file:
+            data = pickle.load(file)
             model = StateModel.model_validate(data)
 
-            if hash(model.config) != hash(config):
-                logger.warning("The configuration in the state file does not match the provided configuration.")
+            if config != model.config and not force:
+                logger.warning(
+                    "The configuration in the state file does not match the provided configuration."
+                )
                 return None
 
             return model
 
-    def save_state(self, state: StateModel) -> None:
+    def save(self, state: StateModel) -> None:
         with self._state_file.open(mode="wb") as f:
-            pickle.dump(state.model_dump(), f)
\ No newline at end of file
+            pickle.dump(state.model_dump(), f)
+
+    def delete(self) -> None:
+        if self._state_file.exists():
+            self._state_file.unlink()
diff --git a/diceplayer/state/state_model.py b/diceplayer/state/state_model.py
index 7a1099f..a7e05b6 100644
--- a/diceplayer/state/state_model.py
+++ b/diceplayer/state/state_model.py
@@ -1,10 +1,19 @@
-from pydantic import BaseModel
-
 from diceplayer.config import PlayerConfig
 from diceplayer.environment import System
 
+from pydantic import BaseModel
+from typing_extensions import Self
+
 
 class StateModel(BaseModel):
     config: PlayerConfig
     system: System
-    current_cycle: int
\ No newline at end of file
+    current_cycle: int
+
+    @classmethod
+    def from_config(cls, config: PlayerConfig) -> Self:
+        return cls(
+            config=config,
+            system=System(),
+            current_cycle=0,
+        )
diff --git a/tests/cli/__init__.py b/tests/cli/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/cli/test_read_input_file.py b/tests/cli/test_read_input_file.py
new file mode 100644
index 0000000..191d797
--- /dev/null
+++ b/tests/cli/test_read_input_file.py
@@ -0,0 +1,30 @@
+import diceplayer
+from diceplayer.cli import read_input
+from diceplayer.config import PlayerConfig
+
+import pytest
+
+from pathlib import Path
+
+
+class TestReadInputFile:
+    @pytest.fixture
+    def example_config(self) -> Path:
+        return Path(diceplayer.__path__[0]).parent / "control.example.yml"
+
+    def test_read_input_file(self, example_config: Path):
+        config = read_input(example_config)
+
+        assert config is not None
+        assert isinstance(config, PlayerConfig)
+
+    def test_read_input_non_existing_file(self):
+        with pytest.raises(FileNotFoundError):
+            read_input("nonexistent_file.yml")
+
+    def test_read_input_invalid_yaml(self, tmp_path: Path):
+        invalid_yaml_file = tmp_path / "invalid.yml"
+        invalid_yaml_file.write_text("This is not valid YAML: [unbalanced brackets")
+
+        with pytest.raises(Exception):
+            read_input(invalid_yaml_file)
diff --git a/tests/state/test_state_handler.py b/tests/state/test_state_handler.py
index 226df9f..b86196f 100644
--- a/tests/state/test_state_handler.py
+++ b/tests/state/test_state_handler.py
@@ -1,10 +1,11 @@
-import tempfile
-from pathlib import Path
+from diceplayer.config import DiceConfig, GaussianConfig, PlayerConfig
+from diceplayer.environment import System
+from diceplayer.state.state_handler import StateHandler
+from diceplayer.state.state_model import StateModel
 
 import pytest
 
-from diceplayer.config import PlayerConfig, DiceConfig, GaussianConfig
-from diceplayer.state.state_handler import StateHandler
+from pathlib import Path
 
 
 class TestStateHandler:
@@ -30,18 +31,87 @@ class TestStateHandler:
             ),
         )
 
-    def test_state_handler_initialization(self):
-        with tempfile.TemporaryDirectory() as tmpdir:
-            tmpdir_path = Path(tmpdir)
-            state_handler = StateHandler(tmpdir_path)
+    def test_initialization(self, tmp_path: Path):
+        state_handler = StateHandler(tmp_path)
 
-            assert isinstance(state_handler, StateHandler)
+        assert isinstance(state_handler, StateHandler)
 
-    def test_state_handler_get_state(self, player_config: PlayerConfig):
-        with tempfile.TemporaryDirectory() as tmpdir:
-            tmpdir_path = Path(tmpdir)
-            state_handler = StateHandler(tmpdir_path)
+    def test_save(self, tmp_path: Path, player_config: PlayerConfig):
+        state_handler = StateHandler(tmp_path)
 
-            state = state_handler.get_state(player_config)
+        state = StateModel(
+            config=player_config,
+            system=System(),
+            current_cycle=0,
+        )
 
-            assert state is None
\ No newline at end of file
+        state_handler.save(state)
+
+        assert (tmp_path / "state.pkl").exists()
+
+    def test_get_when_empty(self, tmp_path: Path, player_config: PlayerConfig):
+        state_handler = StateHandler(tmp_path)
+
+        state = state_handler.get(player_config)
+
+        assert state is None
+
+    def test_get(self, tmp_path: Path, player_config: PlayerConfig):
+        state_handler = StateHandler(tmp_path)
+
+        state = StateModel(
+            config=player_config,
+            system=System(),
+            current_cycle=0,
+        )
+
+        state_handler.save(state)
+
+        retrieved_state = state_handler.get(player_config)
+
+        assert retrieved_state is not None
+        assert retrieved_state.config == state.config
+        assert retrieved_state.system == state.system
+        assert retrieved_state.current_cycle == state.current_cycle
+
+    def test_get_with_different_config(
+        self, tmp_path: Path, player_config: PlayerConfig
+    ):
+        state_handler = StateHandler(tmp_path)
+
+        state = StateModel(
+            config=player_config,
+            system=System(),
+            current_cycle=0,
+        )
+
+        state_handler.save(state)
+
+        different_config = player_config.model_copy(update={"opt": False})
+
+        retrieved_state = state_handler.get(different_config)
+
+        assert retrieved_state is None
+
+    def test_get_with_different_config_force(
+        self, tmp_path: Path, player_config: PlayerConfig
+    ):
+        state_handler = StateHandler(tmp_path)
+
+        state = StateModel(
+            config=player_config,
+            system=System(),
+            current_cycle=0,
+        )
+
+        state_handler.save(state)
+
+        different_config = player_config.model_copy(update={"opt": False})
+
+        retrieved_state = state_handler.get(different_config, force=True)
+
+        assert retrieved_state is not None
+        assert retrieved_state.config == state.config
+        assert retrieved_state.config != different_config
+        assert retrieved_state.system == state.system
+        assert retrieved_state.current_cycle == state.current_cycle