diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..90307d2
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+## ======== Personal ========
+.vscode/
diff --git a/README.md b/README.md
index 8e439ca..52c1d94 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,3 @@
 # LCR Connector
 
-在3个元器件内，使用给定元器件数值列表快速找到目标数值元器件的最好拼接方式，支持电阻，电容，电感
+TODO
diff --git a/legacy/.gitignore b/legacy/.gitignore
new file mode 100644
index 0000000..22dcbb2
--- /dev/null
+++ b/legacy/.gitignore
@@ -0,0 +1,15 @@
+## ======== Personal ========
+
+
+## ======== Python ========
+# Python-generated files
+__pycache__/
+*.py[oc]
+build/
+dist/
+wheels/
+*.egg-info
+
+# Virtual environments
+.venv
+
diff --git a/legacy/.python-version b/legacy/.python-version
new file mode 100644
index 0000000..2c07333
--- /dev/null
+++ b/legacy/.python-version
@@ -0,0 +1 @@
+3.11
diff --git a/legacy/README.md b/legacy/README.md
new file mode 100644
index 0000000..1f0b4a8
--- /dev/null
+++ b/legacy/README.md
@@ -0,0 +1,3 @@
+# LCR Connector (Legacy)
+
+在3个元器件内，使用给定元器件数值列表快速找到目标数值元器件的最好拼接方式，支持电阻，电容，电感
diff --git a/legacy/common.py b/legacy/common.py
new file mode 100644
index 0000000..c7d6679
--- /dev/null
+++ b/legacy/common.py
@@ -0,0 +1,174 @@
+import enum
+from dataclasses import dataclass
+
+class LcrConnException(Exception):
+    """The exception thrown by LCR Connector"""
+    pass
+
+
+class DeviceKind(enum.IntEnum):
+    """The kind of device"""
+    
+    RESISTOR = enum.auto()
+    """Resistor device"""
+    CAPACITOR = enum.auto()
+    """Capacitor device"""
+    INDUCTOR = enum.auto()
+    """Inductor device"""
+
+
+class JointKind(enum.IntEnum):
+    """The joint type between 2 devices"""
+    
+    SERIES = enum.auto()
+    """Series connection"""
+    PARALLEL = enum.auto()
+    """Parallel connection"""
+    
+    def flip(self) -> 'JointKind':
+        """
+        Flip the joint kind
+        
+        Flip the joint kind from series to parallel or vice versa
+
+        :return: The flipped joint kind
+        """
+        match self:
+            case JointKind.SERIES:
+                return JointKind.PARALLEL
+            case JointKind.PARALLEL:
+                return JointKind.SERIES
+
+
+@dataclass
+class CircuitJoint:
+    """The part of circuit composed of two devices and the joint kind"""
+
+    device_value: float
+    """The value of the device"""
+    joint_kind: JointKind
+    """The joint kind between this device and the next device"""
+    
+    def compute(self, value: float,  device_kind: DeviceKind) -> float:
+        """
+        Compute the joint value
+
+        :param value: The value computed from previous devices
+        :param device_kind: The kind of the device
+        :return: The joint value computed
+        """
+        if self.device_value <= 0 or value <= 0:
+            raise LcrConnException("Device value must be greater than 0")
+        
+        # We perform series connect for: series resistor, series inductor and parallel capacitor.
+        # We perform parallel connect for: parallel resistor, parallel inductor and series capacitor.
+        joint_kind = self.joint_kind
+        if device_kind == DeviceKind.CAPACITOR:
+            joint_kind = joint_kind.flip()
+
+        match joint_kind:
+            case JointKind.SERIES:
+                return self.device_value + value
+            case JointKind.PARALLEL:
+                return (self.device_value * value) / (self.device_value + value)
+
+
+class Circuit:
+    """The circuit composed of multiple joints"""
+
+    device_value: float
+    """The value of the first device"""
+    joints: list[CircuitJoint]
+    """The joints between devices"""
+
+    def __init__(self, value: float):
+        self.device_value = value
+        self.joints = []
+
+    def add_joint(self, joint: CircuitJoint):
+        self.joints.append(joint)
+
+    def len_devices(self) -> int:
+        return len(self.joints) + 1
+
+    def compute(self, device_kind: DeviceKind) -> float:
+        """
+        Compute the circuit value
+
+        :param device_kind: The kind of the device
+        :return: The circuit value
+        """
+        if self.device_value <= 0:
+            raise LcrConnException("Device value must be greater than 0")
+        
+        value = self.device_value
+        for joint in self.joints:
+            value = joint.compute(value, device_kind)
+        return value
+        
+
+def from_human_readable_value(strl: str) -> float:
+    """
+    Convert human readable value to float
+
+    :param strl: The human readable value
+    :return: The parsed float value
+    :raises ValueError: If the input string is not a valid number
+    """
+    strl = strl.strip()
+
+    if strl.endswith('n'):
+        return float(strl[0:-1]) * 1e-12
+    if strl.endswith('p'):
+        return float(strl[0:-1]) * 1e-9
+    if strl.endswith('u'):
+        return float(strl[0:-1]) * 1e-6
+    if strl.endswith('m'):
+        return float(strl[0:-1]) * 1e-3
+    if strl.endswith('k'):
+        return float(strl[0:-1]) * 1e3
+    if strl.endswith('M'):
+        return float(strl[0:-1]) * 1e6
+    if strl.endswith('G'):
+        return float(strl[0:-1]) * 1e9
+    return float(strl)
+
+
+
+def to_human_readable_value(v: float) -> str:
+    """
+    Convert float value to human readable value
+
+    :param value: The float value
+    :return: The human readable value
+    """
+    if v / 1e-12 < 1e3:
+        return "{:e} n".format(v / 1e-12)
+    if v / 1e-9 < 1e3:
+        return "{:.4f} p".format(v / 1e-9)
+    if v / 1e-6 < 1e3:
+        return "{:.4f} u".format(v / 1e-6)
+    if v / 1e-3 < 1e3:
+        return "{:.4f} m".format(v / 1e-3)
+    if v < 1e3:
+        return "{:.4f}".format(v)
+    if v / 1e3 < 1e3:
+        return "{:.4f} k".format(v / 1e3)
+    if v / 1e6 < 1e3:
+        return "{:.4f} M".format(v / 1e6)
+    if v / 1e9 < 1e3:
+        return "{:.4f} G".format(v / 1e9)
+
+    return "{:e}".format(v)
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/legacy/dataset.py b/legacy/dataset.py
new file mode 100644
index 0000000..d71c6bc
--- /dev/null
+++ b/legacy/dataset.py
@@ -0,0 +1,61 @@
+from typing import Iterable
+from pathlib import Path
+from dataclasses import dataclass
+from .common import LcrConnException, from_human_readable_value
+
+
+@dataclass(frozen=True)
+class DataSubset:
+    """A list holding available device gauge values for resistor, capacitor or inductor"""
+
+    gauges: tuple[float, ...]
+    """A list of available device gauge values"""
+
+    @staticmethod
+    def from_iterable(str_gauges: Iterable[str]) -> "DataSubset":
+        # Remove redundant parts
+        gauges_set: set[float] = set()
+        for str_gauge in str_gauges:
+            numeric_gauge = from_human_readable_value(str_gauge)
+            if numeric_gauge in gauges_set:
+                raise LcrConnException(f"Duplicate gauge value found: {str_gauge}")
+            else:
+                gauges_set.add(numeric_gauge)
+        # Return value
+        return DataSubset(tuple(gauges_set))
+
+    @staticmethod
+    def from_file(filename: Path) -> "DataSubset":
+        with open(filename, "r", encoding="utf-8") as f:
+            legal_lines = filter(lambda line: line != "", (line.strip() for line in f))
+            return DataSubset.from_iterable(legal_lines)
+
+
+@dataclass(frozen=True)
+class DataSet:
+    """The dataset include 3 lists of available device gauge values for resistor, capacitor and inductor"""
+
+    resistor: DataSubset
+    """A list of available device gauge values for resistor"""
+    capacitor: DataSubset
+    """A list of available device gauge values for capacitor"""
+    inductor: DataSubset
+    """A list of available device gauge values for inductor"""
+
+    @staticmethod
+    def from_iterable(
+        resistor: Iterable[str], capacitor: Iterable[str], inductor: Iterable[str]
+    ) -> "DataSet":
+        return DataSet(
+            DataSubset.from_iterable(resistor),
+            DataSubset.from_iterable(capacitor),
+            DataSubset.from_iterable(inductor),
+        )
+
+    @staticmethod
+    def from_file(resistor: Path, capacitor: Path, inductor: Path) -> "DataSet":
+        return DataSet(
+            DataSubset.from_file(resistor),
+            DataSubset.from_file(capacitor),
+            DataSubset.from_file(inductor),
+        )
diff --git a/legacy/lcr_connector.py b/legacy/lcr_connector.py
new file mode 100644
index 0000000..fc651e5
--- /dev/null
+++ b/legacy/lcr_connector.py
@@ -0,0 +1,36 @@
+from .common import LcrConnException, Circuit, JointKind, to_human_readable_value
+
+
+def _get_joint_kind_symbol(joint_kind: JointKind) -> str:
+    match joint_kind:
+        case JointKind.SERIES:
+            return "S"
+        case JointKind.PARALLEL:
+            return "P"
+
+
+def _illustrate_circuit(circuit: Circuit) -> None:
+    match circuit.len_devices():
+        case 1:
+            dev1 = to_human_readable_value(circuit.device_value)
+            print(f"{dev1}")
+        case 2:
+            dev1 = to_human_readable_value(circuit.device_value)
+            joint1 = circuit.joints[0]
+            j1 = _get_joint_kind_symbol(joint1.joint_kind)
+            dev2 = to_human_readable_value(joint1.device_value)
+            print(f"[{j1}] ┬ {dev1}")
+            print(f"    └ {dev2}")
+        case 3:
+            dev1 = to_human_readable_value(circuit.device_value)
+            joint1 = circuit.joints[0]
+            j1 = _get_joint_kind_symbol(joint1.joint_kind)
+            dev2 = to_human_readable_value(joint1.device_value)
+            joint2 = circuit.joints[1]
+            j2 = _get_joint_kind_symbol(joint2.joint_kind)
+            dev3 = to_human_readable_value(joint2.device_value)
+            print(f"[{j2}] ┬ [{j1}] ┬ {dev1}")
+            print(f"    │     └ {dev2}")
+            print(f"    └ {dev3}")
+        case _:
+            raise LcrConnException("Circuit too complex to illustrate")
diff --git a/main.py b/legacy/main.py
similarity index 100%
rename from main.py
rename to legacy/main.py
diff --git a/legacy/pyproject.toml b/legacy/pyproject.toml
new file mode 100644
index 0000000..f9cf5e2
--- /dev/null
+++ b/legacy/pyproject.toml
@@ -0,0 +1,7 @@
+[project]
+name = "lcr-connector"
+version = "0.1.0"
+description = "Use as much 3 devices to reach target value for resistor, capacitor and inductor."
+readme = "README.md"
+requires-python = ">=3.11"
+dependencies = []
diff --git a/legacy/resolver/__init__.py b/legacy/resolver/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/legacy/resolver/astar.py b/legacy/resolver/astar.py
new file mode 100644
index 0000000..d801962
--- /dev/null
+++ b/legacy/resolver/astar.py
@@ -0,0 +1,15 @@
+from typing import Iterator
+from .common import Resolver, ResolverRequest, ResolverResult, ResultPriority
+from ..dataset import DataSet
+
+class AStarResolver(Resolver):
+    """
+    A resolver that uses A* algorithm to find the best matching circuit.
+    """
+
+    def __init__(self, dataset: DataSet):
+        pass
+
+    
+    def resolve(self, request: ResolverRequest) -> Iterator[ResolverResult]:
+        pass
diff --git a/legacy/resolver/common.py b/legacy/resolver/common.py
new file mode 100644
index 0000000..338acd0
--- /dev/null
+++ b/legacy/resolver/common.py
@@ -0,0 +1,102 @@
+import enum
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import Iterator
+from ..common import DeviceKind, Circuit
+
+
+class ResultPriority(enum.Enum):
+    """
+    The priority of the result.
+    """
+
+    LESS_DEVICES = enum.auto()
+    """Less devices is the first priority."""
+    MORE_ACCURACY = enum.auto()
+    """More accuracy is the first priority."""
+
+
+@dataclass
+class ResolverRequest:
+    """
+    The request object for the resolver.
+    """
+
+    device_kind: DeviceKind
+    """The kind of device to resolve."""
+    target_value: float
+    """The target value of the device."""
+    tolerance: float
+    """The tolerance of the device."""
+    result_priority: ResultPriority
+    """The priority of the result."""
+    count_limit: int
+    """The limit of the count of results."""
+
+
+class ResolverResult:
+    """
+    The result of the resolver.
+    """
+
+    circuit: Circuit
+    """The circuit of the result."""
+
+    __value_cache: float | None
+    """The cache of the circuit value."""
+    __difference_cache: float | None
+    """The cache of the difference between the target value and the circuit value."""
+    __relative_difference_cache: float | None
+    """The cache of the relative difference between the target value and the circuit value."""
+
+    def __init__(self, circuit: Circuit):
+        self.circuit = circuit
+        self.__value_cache = None
+        self.__difference_cache = None
+        self.__relative_difference_cache = None
+
+    def compute(self, device_kind: DeviceKind) -> float:
+        """
+        Compute the circuit value.
+        """
+        if self.__value_cache is None:
+            self.__value_cache = self.circuit.compute(device_kind)
+        return self.__value_cache
+
+    def difference(self, target_value: float, device_kind: DeviceKind) -> float:
+        """
+        Get the difference between the target value and the circuit value.
+        """
+        if self.__difference_cache is None:
+            self.__difference_cache = abs(
+                target_value - self.circuit.compute(device_kind)
+            )
+        return self.__difference_cache
+
+    def relative_difference(
+        self, target_value: float, device_kind: DeviceKind
+    ) -> float:
+        """
+        Get the relative difference between the target value and the circuit value.
+        """
+        if self.__relative_difference_cache is None:
+            self.__relative_difference_cache = (
+                abs(target_value - self.circuit.compute(device_kind)) / target_value
+            )
+        return self.__relative_difference_cache
+
+    def len_devices(self) -> int:
+        """
+        Get the number of devices in the circuit.
+        """
+        return self.circuit.len_devices()
+
+
+class Resolver(ABC):
+    """
+    Abstract base class for all resolvers.
+    """
+
+    @abstractmethod
+    def resolve(self, request: ResolverRequest) -> Iterator[ResolverResult]:
+        pass
diff --git a/legacy/resolver/lut.py b/legacy/resolver/lut.py
new file mode 100644
index 0000000..010e5d9
--- /dev/null
+++ b/legacy/resolver/lut.py
@@ -0,0 +1,109 @@
+import struct
+from typing import Iterator, BinaryIO
+from pathlib import Path
+from .common import Resolver, ResolverRequest, ResolverResult, ResultPriority
+from ..dataset import DataSet
+from ..common import Circuit, CircuitJoint, JointKind, LcrConnException
+
+class LutResolver(Resolver):
+    """
+    A resolver that uses a lookup table to find the best matching circuit.
+    """
+
+    lut: tuple[Circuit]
+
+    def __init__(self, lut: tuple[Circuit]):
+        self.lut = lut
+
+    @staticmethod
+    def from_dataset(dataset: DataSet) -> 'LutResolver':
+        pass
+
+    @staticmethod
+    def from_cache(filename: Path) -> 'LutResolver':
+        with open(filename, "rb") as f:
+            cnt = _read_int(f)
+            return LutResolver(tuple(LutItem.from_cache(f) for _ in range(cnt)))
+    
+    def save_as_cache(self, filename: Path) -> None:
+        with open(filename, "wb") as f:
+            _write_int(f, len(self.lut))
+            for item in self.lut:
+                item.save_as_cache(f)
+
+    def resolve(self, request: ResolverRequest) -> Iterator[ResolverResult]:
+        pass
+
+
+class LutItem:
+    """
+    An item in the lookup table.
+    """
+
+    circuit: Circuit
+    """The circuit represented by this item."""
+    __value_cache: float | None
+    """The cached computed value of the circuit, or None if it has not been cached yet."""
+
+    def __init__(self, circuit: Circuit):
+        self.circuit = circuit
+
+    @staticmethod
+    def from_cache(f: BinaryIO) -> 'LutItem':
+        cnt = _read_int(f)
+
+        if cnt < 1:
+            raise LcrConnException("Invalid circuit count in LUT item")
+        device_value = _read_double(f)
+        circuit = Circuit(device_value)
+        cnt -= 1
+
+        for _ in range(cnt):
+            j = JointKind.SERIES if _read_bool(f) else JointKind.PARALLEL
+            dev = _read_double(f)
+            joint = CircuitJoint(j, dev)
+            circuit.add_joint(joint)
+        
+        return LutItem(circuit)
+
+    def save_as_cache(self, f: BinaryIO) -> None:
+        _write_int(f, self.circuit.len_devices())
+        _write_double(f, self.circuit.device_value)
+        for joint in self.circuit.joints():
+            _write_bool(f, joint.kind == JointKind.SERIES)
+            _write_double(f, joint.value)
+
+    def compute(self) -> float:
+        """The computed value of the circuit."""
+        if self.__value_cache is None:
+            self.__value_cache = self.circuit.value()
+        return self.__value_cache
+
+
+
+DOUBLE_PACKER = struct.Struct("d")
+INT_PACKER = struct.Struct("I")
+BOOL_PACKER = struct.Struct("?")
+
+def _read_double(fs) -> float:
+    return DOUBLE_PACKER.unpack(fs.read(DOUBLE_PACKER.size))[0]
+
+def _read_int(fs) -> int:
+    return INT_PACKER.unpack(fs.read(INT_PACKER.size))[0]
+
+def _read_bool(fs) -> bool:
+    return BOOL_PACKER.unpack(fs.read(BOOL_PACKER.size))[0]
+
+def _write_double(fs, num: float):
+    fs.write(DOUBLE_PACKER.pack(num))
+
+def _write_int(fs, num: int):
+    fs.write(INT_PACKER.pack(num))
+
+def _write_bool(fs, num: bool):
+    fs.write(BOOL_PACKER.pack(num))
+
+
+
+
+
diff --git a/legacy/uv.lock b/legacy/uv.lock
new file mode 100644
index 0000000..c774378
--- /dev/null
+++ b/legacy/uv.lock
@@ -0,0 +1,8 @@
+version = 1
+revision = 2
+requires-python = ">=3.11"
+
+[[package]]
+name = "lcr-connector"
+version = "0.1.0"
+source = { virtual = "." }