diff --git a/index.ts b/index.ts
new file mode 100644
index 0000000..3695555
--- /dev/null
+++ b/index.ts
@@ -0,0 +1,173 @@
+// Type Definitions
+type HttpMethod = 'GET' | 'POST';
+type UserRole = 'user' | 'admin';
+
+interface User {
+  name: string;
+  age: number;
+  roles: UserRole[];
+  createdAt: Date;
+  isDeleated: boolean;
+}
+
+interface RequestBase {
+  method: HttpMethod;
+  host: string;
+  path: string;
+  params?: Record<string, any>;
+}
+
+interface PostRequest extends RequestBase {
+  method: 'POST';
+  body: User;
+}
+
+interface GetRequest extends RequestBase {
+  method: 'GET';
+}
+
+type Request = PostRequest | GetRequest;
+
+interface Response {
+  status: number;
+}
+
+interface ObserverHandlers<T> {
+  next?: (value: T) => void;
+  error?: (error: unknown) => void;
+  complete?: () => void;
+}
+
+interface Subscription {
+  unsubscribe(): void;
+}
+
+// Observer Class
+class Observer<T> {
+  private isUnsubscribed = false;
+  private _unsubscribe?: () => void;
+
+  constructor(private handlers: ObserverHandlers<T>) {}
+
+  next(value: T): void {
+    if (!this.isUnsubscribed && this.handlers.next) {
+      this.handlers.next(value);
+    }
+  }
+
+  error(error: unknown): void {
+    if (!this.isUnsubscribed) {
+      if (this.handlers.error) {
+        this.handlers.error(error);
+      }
+      this.unsubscribe();
+    }
+  }
+
+  complete(): void {
+    if (!this.isUnsubscribed) {
+      if (this.handlers.complete) {
+        this.handlers.complete();
+      }
+      this.unsubscribe();
+    }
+  }
+
+  unsubscribe(): void {
+    this.isUnsubscribed = true;
+    if (this._unsubscribe) {
+      this._unsubscribe();
+    }
+  }
+
+  setUnsubscribe(unsub: () => void) {
+    this._unsubscribe = unsub;
+  }
+}
+
+// Observable Class
+class Observable<T> {
+  constructor(private _subscribeFn: (observer: Observer<T>) => () => void) {}
+
+  static from<T>(values: T[]): Observable<T> {
+    return new Observable<T>((observer: Observer<T>) => {
+      values.forEach((value) => observer.next(value));
+      observer.complete();
+
+      return () => {
+        console.log('unsubscribed');
+      };
+    });
+  }
+
+  subscribe(handlers: ObserverHandlers<T>): Subscription {
+    const observer = new Observer<T>(handlers);
+    const unsub = this._subscribeFn(observer);
+    observer.setUnsubscribe(unsub);
+
+    return {
+      unsubscribe: () => observer.unsubscribe()
+    };
+  }
+}
+
+// Constants
+const HTTP_POST_METHOD: HttpMethod = 'POST';
+const HTTP_GET_METHOD: HttpMethod = 'GET';
+
+const HTTP_STATUS_OK = 200;
+const HTTP_STATUS_INTERNAL_SERVER_ERROR = 500;
+
+// Mock Data
+const userMock: User = {
+  name: 'User Name',
+  age: 26,
+  roles: ['user', 'admin'],
+  createdAt: new Date(),
+  isDeleated: false,
+};
+
+const requestsMock: Request[] = [
+  {
+    method: HTTP_POST_METHOD,
+    host: 'service.example',
+    path: 'user',
+    body: userMock,
+    params: {},
+  },
+  {
+    method: HTTP_GET_METHOD,
+    host: 'service.example',
+    path: 'user',
+    params: {
+      id: '3f5h67s4s',
+    },
+  }
+];
+
+// Handlers
+const handleRequest = (request: Request): Response => {
+  // Simulate request handling
+  console.log('Request handled:', request);
+  return { status: HTTP_STATUS_OK };
+};
+
+const handleError = (error: unknown): Response => {
+  console.error('Error occurred:', error);
+  return { status: HTTP_STATUS_INTERNAL_SERVER_ERROR };
+};
+
+const handleComplete = (): void => {
+  console.log('complete');
+};
+
+// Usage
+const requests$ = Observable.from<Request>(requestsMock);
+const subscription = requests$.subscribe({
+  next: handleRequest,
+  error: handleError,
+  complete: handleComplete
+});
+
+// Unsubscribe explicitly
+subscription.unsubscribe();