diff --git a/README.md b/README.md
index 6946e76..956512c 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,9 @@
 # fvr
 
 fvr; a suite of tools designed to enhance efficiency and productivity.
+
+Example usage:
+- `fvr.geom.polygon(vertices).area`
+- `fvr.wire.awg(number)`
+- `fvr.wire.awg(number).diameter`
+- `fvr.wire.awg(number).area`
diff --git a/src/fvr/geom.py b/src/fvr/geom.py
index d32cfdb..6551fc4 100644
--- a/src/fvr/geom.py
+++ b/src/fvr/geom.py
@@ -1,19 +1,40 @@
+import re
 from fvr.typing import FloatArray
 
-def area(vertices: FloatArray) -> float:
-  r"""Determine the area of a simple polygon.
+class polygon:
+  def __init__(self, vertices: FloatArray|str):
+    r"""Properties of a simple polygon.
 
-  Args:
-    vertices: List of points, pair of x and y: "[[x1, y1], [x2, y2], ...]"
-  
-  Shoelace formula, Gauss's area formula, surveyor's formula
+    Args:
+      vertices: List of points, pair of x and y: "[[x1, y1], [x2, y2], ...]"
+    """
+    if isinstance(vertices, str):
+      vertices = self.str2arr(vertices)
+    self.vertices = vertices
 
-  https://en.wikipedia.org/wiki/Shoelace_formula
-  """
-  count = len(vertices)  # of corners
-  result = 0.0
-  for i in range(count):
-    j = (i + 1) % count
-    result += vertices[i][0] * vertices[j][1] - vertices[i][1] * vertices[j][0]
-  result = abs(result) / 2.0
-  return result
+  @staticmethod
+  def str2arr(vertices: str) -> list:
+    strm = re.match(r'\[.*\]', ''.join(vertices))
+    if strm and strm.group():
+      return eval(strm.group())
+
+  @property
+  def area(self) -> float:
+    r"""Determine the area of a simple polygon.
+
+    Example:
+      >>> fvr.geom.polygon([[0, 0], [0, 1], [1, 1], [1, 0]]).area
+      >>> fvr.geom.polygon('[[0, 0], [0, 1], [1, 1], [1, 0]]').area
+
+    Shoelace formula, Gauss's area formula, surveyor's formula
+
+    https://en.wikipedia.org/wiki/Shoelace_formula
+    """
+    count = len(self.vertices)  # of corners
+    result = 0.0
+    for i in range(count):
+      j = (i + 1) % count
+      result += self.vertices[i][0] * self.vertices[j][1] - \
+        self.vertices[i][1] * self.vertices[j][0]
+    result = abs(result) / 2.0
+    return result
diff --git a/src/fvr/wire.py b/src/fvr/wire.py
index 48b3ef6..a3d9c2e 100644
--- a/src/fvr/wire.py
+++ b/src/fvr/wire.py
@@ -10,18 +10,20 @@ class awg:
       number: AWG wire size, also '00', '000', '0000'
     """
     self.number = number
-    self.num2int()
+    self._number = self.num2int(number)
 
-  def num2int(self):
-    if isinstance(self.number, int):
-      self._number = self.number
-    elif self.number.isdigit():
-      if self.number in ['00', '000', '0000']:
-        self._number = 1 - len(self.number)
+  @staticmethod
+  def num2int(number: int|str):
+    if isinstance(number, int):
+      res = number
+    elif number.isdigit():
+      if number in ['00', '000', '0000']:
+        res = 1 - len(number)
       else:
-        self._number = int(self.number)
+        res = int(number)
     else:
-      raise ValueError
+      raise ValueError(f"{number} is not a number.")
+    return res
 
   @property
   def diameter(self):