diff --git a/src/App.css b/src/App.css
index 9838c73..9ecf8f2 100644
--- a/src/App.css
+++ b/src/App.css
@@ -1,7 +1,7 @@
 .todo-container {
-  max-width: 540px;
+  max-width: 560px;
   width: 100%;
-  margin: 60px auto;
+  margin: 50px auto;
   padding: 32px;
   background: var(--bg);
   border: 1px solid var(--border);
@@ -21,88 +21,178 @@
 
 .input-section {
   display: flex;
-  gap: 12px;
-  margin-bottom: 24px;
+  flex-direction: column;
+  gap: 16px;
+  margin-bottom: 28px;
+  background: var(--code-bg);
+  padding: 20px;
+  border-radius: 12px;
+  border: 1px solid var(--border);
 }
 
-.input-section input {
-  flex: 1;
-  padding: 12px 16px;
+.task-input-wrapper {
+  width: 100%;
+}
+
+.task-input {
+  width: 100%;
+  padding: 14px 16px;
   font-size: 16px;
   border: 1px solid var(--border);
   border-radius: 8px;
-  background: var(--code-bg);
+  background: var(--bg);
   color: var(--text-h);
   outline: none;
+  box-sizing: border-box;
   transition: border-color 0.2s, box-shadow 0.2s;
 }
 
-.input-section input:focus {
+.task-input:focus,
+.reminder-input:focus {
   border-color: var(--accent);
   box-shadow: 0 0 0 3px var(--accent-bg);
 }
 
-.input-section button {
-  padding: 12px 20px;
-  font-size: 16px;
+.task-input.input-error {
+  border-color: #ef4444;
+  box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.15);
+}
+
+.reminder-section {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+}
+
+.reminder-label {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  font-size: 13px;
+  font-weight: 600;
+  color: var(--text-h);
+}
+
+.label-icon {
+  font-size: 14px;
+}
+
+.reminder-controls {
+  display: flex;
+  gap: 12px;
+  align-items: center;
+}
+
+.reminder-input {
+  flex: 1;
+  padding: 12px 14px;
+  font-size: 14px;
+  font-family: inherit;
+  border: 1px solid var(--border);
+  border-radius: 8px;
+  background: var(--bg);
+  color: var(--text-h);
+  outline: none;
+  box-sizing: border-box;
+  transition: border-color 0.2s, box-shadow 0.2s;
+}
+
+.add-btn {
+  padding: 12px 24px;
+  font-size: 15px;
   font-weight: 600;
   background: var(--accent);
   color: #ffffff;
   border: none;
   border-radius: 8px;
   cursor: pointer;
+  white-space: nowrap;
   transition: opacity 0.2s, transform 0.1s;
 }
 
-.input-section button:hover {
+.add-btn:hover {
   opacity: 0.9;
 }
 
-.input-section button:active {
+.add-btn:active {
   transform: scale(0.98);
 }
 
+.error-message {
+  margin: 0;
+  color: #ef4444;
+  font-size: 14px;
+  font-weight: 500;
+}
+
 .todo-container ul {
   list-style: none;
   padding: 0;
   margin: 0;
   display: flex;
   flex-direction: column;
-  gap: 10px;
+  gap: 12px;
 }
 
 .todo-container li {
   display: flex;
   align-items: center;
   justify-content: space-between;
-  padding: 12px 16px;
+  padding: 14px 16px;
   background: var(--code-bg);
   border: 1px solid var(--border);
-  border-radius: 8px;
+  border-radius: 10px;
   transition: background-color 0.2s, border-color 0.2s;
 }
 
-.todo-container li span {
+.task-content {
   flex: 1;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
   cursor: pointer;
-  color: var(--text-h);
-  font-size: 16px;
   user-select: none;
-  transition: color 0.2s, text-decoration 0.2s;
-  word-break: break-word;
 }
 
-.todo-container li span:hover {
+.task-text {
+  color: var(--text-h);
+  font-size: 16px;
+  font-weight: 500;
+  word-break: break-word;
+  transition: color 0.2s, text-decoration 0.2s;
+}
+
+.task-content:hover .task-text {
   color: var(--accent);
 }
 
-.todo-container li.completed span {
+.task-timestamps {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 12px;
+  font-size: 12px;
+  color: var(--text);
+  opacity: 0.85;
+}
+
+.task-created,
+.task-reminder {
+  display: inline-flex;
+  align-items: center;
+}
+
+.todo-container li.completed .task-text {
   text-decoration: line-through;
   color: var(--text);
   opacity: 0.6;
 }
 
-.todo-container li button {
+.todo-container li.completed .task-timestamps {
+  text-decoration: line-through;
+  opacity: 0.4;
+}
+
+.delete-btn {
   padding: 6px 12px;
   font-size: 14px;
   background: transparent;
@@ -114,8 +204,22 @@
   transition: background-color 0.2s, color 0.2s, border-color 0.2s;
 }
 
-.todo-container li button:hover {
+.delete-btn:hover {
   background: #ef4444;
   color: #ffffff;
   border-color: #ef4444;
 }
+
+@media (max-width: 520px) {
+  .reminder-controls {
+    flex-direction: column;
+    align-items: stretch;
+  }
+  .add-btn {
+    width: 100%;
+  }
+  .task-timestamps {
+    flex-direction: column;
+    gap: 4px;
+  }
+}
diff --git a/src/App.jsx b/src/App.jsx
index 74a879d..81cc2b3 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -1,56 +1,179 @@
-import { useState } from "react";
+import { useState, useEffect } from "react";
 import "./App.css";
 
 function App() {
   const [task, setTask] = useState("");
+  const [reminder, setReminder] = useState("");
   const [tasks, setTasks] = useState([]);
+  const [error, setError] = useState("");
 
-  const addTask = () => {
-    if (task.trim() === "") return;
+  const addTask = async () => {
+    if (task.trim() === "") {
+      setError("Please enter a task name.");
+      return;
+    }
+
+    let reminderIso = null;
+    if (reminder) {
+      const selectedDate = new Date(reminder);
+      if (!isNaN(selectedDate.getTime())) {
+        reminderIso = selectedDate.toISOString();
+      }
+
+      // Requirement: Ask for notification permission only when setting a reminder
+      if ("Notification" in window && Notification.permission === "default") {
+        try {
+          await Notification.requestPermission();
+        } catch (err) {
+          console.error("Notification permission error:", err);
+        }
+      }
+    }
 
     const newTask = {
-      text: task,
+      id: Date.now() + Math.random(),
+      text: task.trim(),
       completed: false,
+      createdAt: new Date().toISOString(),
+      reminder: reminderIso,
+      reminderFired: false,
     };
 
-    setTasks([...tasks, newTask]);
+    setTasks((prev) => [...prev, newTask]);
     setTask("");
+    setReminder("");
+    setError("");
   };
 
-  const deleteTask = (index) => {
-    setTasks(tasks.filter((_, i) => i !== index));
+  const deleteTask = (id) => {
+    setTasks((prev) => prev.filter((item) => item.id !== id));
   };
 
-  const toggleTask = (index) => {
-    setTasks(
-      tasks.map((item, i) =>
-        i === index ? { ...item, completed: !item.completed } : item
+  const toggleTask = (id) => {
+    setTasks((prev) =>
+      prev.map((item) =>
+        item.id === id ? { ...item, completed: !item.completed } : item
       )
     );
   };
 
+  useEffect(() => {
+    const interval = setInterval(() => {
+      const now = new Date().getTime();
+
+      setTasks((prevTasks) => {
+        let updated = false;
+        const nextTasks = prevTasks.map((item) => {
+          if (
+            item.reminder &&
+            !item.reminderFired &&
+            !item.completed &&
+            new Date(item.reminder).getTime() <= now
+          ) {
+            updated = true;
+
+            if ("Notification" in window && Notification.permission === "granted") {
+              try {
+                new Notification("Task Reminder", {
+                  body: `Reminder: ${item.text}`,
+                });
+              } catch (e) {
+                console.error("Notification failed:", e);
+              }
+            }
+
+            alert(`Reminder: ${item.text}`);
+
+            return { ...item, reminderFired: true };
+          }
+          return item;
+        });
+
+        return updated ? nextTasks : prevTasks;
+      });
+    }, 3000);
+
+    return () => clearInterval(interval);
+  }, []);
+
+  const formatDate = (isoString) => {
+    if (!isoString) return "";
+    const date = new Date(isoString);
+    if (isNaN(date.getTime())) return isoString;
+
+    const day = date.getDate();
+    const month = date.toLocaleString("en-US", { month: "short" });
+    const year = date.getFullYear();
+    const time = date.toLocaleString("en-US", {
+      hour: "2-digit",
+      minute: "2-digit",
+      hour12: true,
+    });
+
+    return `${day} ${month} ${year}, ${time}`;
+  };
+
   return (
     <div className="todo-container">
       <h1>To-Do List</h1>
 
       <div className="input-section">
-        <input
-          type="text"
-          placeholder="Enter a task..."
-          value={task}
-          onChange={(e) => setTask(e.target.value)}
-          onKeyDown={(e) => e.key === "Enter" && addTask()}
-        />
+        <div className="task-input-wrapper">
+          <input
+            type="text"
+            className={`task-input ${error ? "input-error" : ""}`}
+            placeholder="Enter a task..."
+            value={task}
+            onChange={(e) => {
+              setTask(e.target.value);
+              if (error) setError("");
+            }}
+            onKeyDown={(e) => e.key === "Enter" && addTask()}
+          />
+        </div>
 
-        <button onClick={addTask}>Add</button>
+        <div className="reminder-section">
+          <label className="reminder-label">
+            <span className="label-icon">📅</span> Reminder (Optional)
+          </label>
+          <div className="reminder-controls">
+            <input
+              type="datetime-local"
+              className="reminder-input"
+              value={reminder}
+              onChange={(e) => setReminder(e.target.value)}
+              onKeyDown={(e) => e.key === "Enter" && addTask()}
+            />
+            <button className="add-btn" onClick={addTask}>
+              Add Task
+            </button>
+          </div>
+        </div>
+
+        {error && <p className="error-message">{error}</p>}
       </div>
 
       <ul>
-        {tasks.map((item, index) => (
-          <li key={index} className={item.completed ? "completed" : ""}>
-            <span onClick={() => toggleTask(index)}>{item.text}</span>
+        {tasks.map((item) => (
+          <li key={item.id} className={item.completed ? "completed" : ""}>
+            <div className="task-content" onClick={() => toggleTask(item.id)}>
+              <span className="task-text">{item.text}</span>
 
-            <button onClick={() => deleteTask(index)}>Delete</button>
+              <div className="task-timestamps">
+                <span className="task-created">
+                  Added: {formatDate(item.createdAt)}
+                </span>
+                <span className="task-reminder">
+                  {item.reminder
+                    ? `🔔 Reminder: ${formatDate(item.reminder)}`
+                    : "No reminder set"}
+                </span>
+              </div>
+            </div>
+
+            <button className="delete-btn" onClick={() => deleteTask(item.id)}>
+              Delete
+            </button>
           </li>
         ))}
       </ul>