Adding attributes

src/geometry/Circle.ts

@@ -45,6 +45,10 @@ export default class Circle extends Shape {
     };
   }
 
+  area() {
+    return Math.PI * this.radius * this.radius;
+  }
+
   static fromAttributes(attributes: CircleAttributes): Circle {
     const { radius } = attributes;
     return new Circle(radius);

src/geometry/Rectangle.ts

@@ -45,6 +45,10 @@ export default class Rectangle extends Shape {
     return new Rectangle(width, height);
   }
 
+  area() {
+    return this.width * this.height
+  }
+
   get attributeData() {
     return [
       {

src/geometry/Square.ts

@@ -38,6 +38,10 @@ export default class Square extends Rectangle {
     );
   }
 
+  area() {
+    return this.sideLength * this.sideLength;
+  }
+
   getCloneAttributes() {
     return [this.sideLength];
   }