diff --git a/backend/main.py b/backend/main.py
index 7a4f18b..67b47a0 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -1,11 +1,12 @@
 from contextlib import asynccontextmanager
-from fastapi import FastAPI, Depends, HTTPException, Response, status
+from fastapi import FastAPI, Depends, HTTPException, Response, status, Query
 from fastapi.middleware.cors import CORSMiddleware
-from sqlalchemy import select
+from sqlalchemy import select, func, desc
 from sqlalchemy.ext.asyncio import AsyncSession
 
+from pydantic import BaseModel
 from database import engine, get_db, Base
-from models import Counter, User
+from models import Counter, User, SumRecord, CounterRecord
 from auth import (
     ACCESS_TOKEN_EXPIRE_MINUTES,
     COOKIE_NAME,
@@ -129,10 +130,175 @@ async def get_counter(
 @app.post("/api/counter/increment")
 async def increment_counter(
     db: AsyncSession = Depends(get_db),
-    _current_user: User = Depends(get_current_user),
+    current_user: User = Depends(get_current_user),
 ):
     counter = await get_or_create_counter(db)
+    value_before = counter.value
     counter.value += 1
+    
+    record = CounterRecord(
+        user_id=current_user.id,
+        value_before=value_before,
+        value_after=counter.value,
+    )
+    db.add(record)
     await db.commit()
     return {"value": counter.value}
 
+
+# Sum endpoints
+class SumRequest(BaseModel):
+    a: float
+    b: float
+
+
+class SumResponse(BaseModel):
+    a: float
+    b: float
+    result: float
+
+
+@app.post("/api/sum", response_model=SumResponse)
+async def calculate_sum(
+    data: SumRequest,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+):
+    result = data.a + data.b
+    record = SumRecord(
+        user_id=current_user.id,
+        a=data.a,
+        b=data.b,
+        result=result,
+    )
+    db.add(record)
+    await db.commit()
+    return SumResponse(a=data.a, b=data.b, result=result)
+
+
+# Audit endpoints
+from datetime import datetime
+from typing import List
+
+
+class CounterRecordResponse(BaseModel):
+    id: int
+    user_email: str
+    value_before: int
+    value_after: int
+    created_at: datetime
+
+
+class SumRecordResponse(BaseModel):
+    id: int
+    user_email: str
+    a: float
+    b: float
+    result: float
+    created_at: datetime
+
+
+class PaginatedCounterRecords(BaseModel):
+    records: List[CounterRecordResponse]
+    total: int
+    page: int
+    per_page: int
+    total_pages: int
+
+
+class PaginatedSumRecords(BaseModel):
+    records: List[SumRecordResponse]
+    total: int
+    page: int
+    per_page: int
+    total_pages: int
+
+
+@app.get("/api/audit/counter", response_model=PaginatedCounterRecords)
+async def get_counter_records(
+    page: int = Query(1, ge=1),
+    per_page: int = Query(10, ge=1, le=100),
+    db: AsyncSession = Depends(get_db),
+    _current_user: User = Depends(get_current_user),
+):
+    # Get total count
+    count_result = await db.execute(select(func.count(CounterRecord.id)))
+    total = count_result.scalar() or 0
+    total_pages = (total + per_page - 1) // per_page if total > 0 else 1
+
+    # Get paginated records with user email
+    offset = (page - 1) * per_page
+    query = (
+        select(CounterRecord, User.email)
+        .join(User, CounterRecord.user_id == User.id)
+        .order_by(desc(CounterRecord.created_at))
+        .offset(offset)
+        .limit(per_page)
+    )
+    result = await db.execute(query)
+    rows = result.all()
+
+    records = [
+        CounterRecordResponse(
+            id=record.id,
+            user_email=email,
+            value_before=record.value_before,
+            value_after=record.value_after,
+            created_at=record.created_at,
+        )
+        for record, email in rows
+    ]
+
+    return PaginatedCounterRecords(
+        records=records,
+        total=total,
+        page=page,
+        per_page=per_page,
+        total_pages=total_pages,
+    )
+
+
+@app.get("/api/audit/sum", response_model=PaginatedSumRecords)
+async def get_sum_records(
+    page: int = Query(1, ge=1),
+    per_page: int = Query(10, ge=1, le=100),
+    db: AsyncSession = Depends(get_db),
+    _current_user: User = Depends(get_current_user),
+):
+    # Get total count
+    count_result = await db.execute(select(func.count(SumRecord.id)))
+    total = count_result.scalar() or 0
+    total_pages = (total + per_page - 1) // per_page if total > 0 else 1
+
+    # Get paginated records with user email
+    offset = (page - 1) * per_page
+    query = (
+        select(SumRecord, User.email)
+        .join(User, SumRecord.user_id == User.id)
+        .order_by(desc(SumRecord.created_at))
+        .offset(offset)
+        .limit(per_page)
+    )
+    result = await db.execute(query)
+    rows = result.all()
+
+    records = [
+        SumRecordResponse(
+            id=record.id,
+            user_email=email,
+            a=record.a,
+            b=record.b,
+            result=record.result,
+            created_at=record.created_at,
+        )
+        for record, email in rows
+    ]
+
+    return PaginatedSumRecords(
+        records=records,
+        total=total,
+        page=page,
+        per_page=per_page,
+        total_pages=total_pages,
+    )
+
diff --git a/backend/models.py b/backend/models.py
index 7251bf8..02c052a 100644
--- a/backend/models.py
+++ b/backend/models.py
@@ -1,4 +1,5 @@
-from sqlalchemy import Integer, String
+from datetime import datetime
+from sqlalchemy import Integer, String, Float, DateTime, ForeignKey
 from sqlalchemy.orm import Mapped, mapped_column
 from database import Base
 
@@ -17,3 +18,24 @@ class User(Base):
     email: Mapped[str] = mapped_column(String(255), unique=True, nullable=False, index=True)
     hashed_password: Mapped[str] = mapped_column(String(255), nullable=False)
 
+
+class SumRecord(Base):
+    __tablename__ = "sum_records"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id: Mapped[int] = mapped_column(Integer, ForeignKey("users.id"), nullable=False, index=True)
+    a: Mapped[float] = mapped_column(Float, nullable=False)
+    b: Mapped[float] = mapped_column(Float, nullable=False)
+    result: Mapped[float] = mapped_column(Float, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
+
+class CounterRecord(Base):
+    __tablename__ = "counter_records"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
+    user_id: Mapped[int] = mapped_column(Integer, ForeignKey("users.id"), nullable=False, index=True)
+    value_before: Mapped[int] = mapped_column(Integer, nullable=False)
+    value_after: Mapped[int] = mapped_column(Integer, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow)
+
diff --git a/frontend/app/audit/page.tsx b/frontend/app/audit/page.tsx
new file mode 100644
index 0000000..dfe714d
--- /dev/null
+++ b/frontend/app/audit/page.tsx
@@ -0,0 +1,428 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { useRouter } from "next/navigation";
+import { useAuth } from "../auth-context";
+import { API_URL } from "../config";
+
+interface CounterRecord {
+  id: number;
+  user_email: string;
+  value_before: number;
+  value_after: number;
+  created_at: string;
+}
+
+interface SumRecord {
+  id: number;
+  user_email: string;
+  a: number;
+  b: number;
+  result: number;
+  created_at: string;
+}
+
+interface PaginatedResponse<T> {
+  records: T[];
+  total: number;
+  page: number;
+  per_page: number;
+  total_pages: number;
+}
+
+export default function AuditPage() {
+  const [counterData, setCounterData] = useState<PaginatedResponse<CounterRecord> | null>(null);
+  const [sumData, setSumData] = useState<PaginatedResponse<SumRecord> | null>(null);
+  const [counterPage, setCounterPage] = useState(1);
+  const [sumPage, setSumPage] = useState(1);
+  const { user, isLoading, logout } = useAuth();
+  const router = useRouter();
+
+  useEffect(() => {
+    if (!isLoading && !user) {
+      router.push("/login");
+    }
+  }, [isLoading, user, router]);
+
+  useEffect(() => {
+    if (user) {
+      fetchCounterRecords(counterPage);
+    }
+  }, [user, counterPage]);
+
+  useEffect(() => {
+    if (user) {
+      fetchSumRecords(sumPage);
+    }
+  }, [user, sumPage]);
+
+  const fetchCounterRecords = async (page: number) => {
+    try {
+      const res = await fetch(`${API_URL}/api/audit/counter?page=${page}&per_page=10`, {
+        credentials: "include",
+      });
+      const data = await res.json();
+      setCounterData(data);
+    } catch {
+      setCounterData(null);
+    }
+  };
+
+  const fetchSumRecords = async (page: number) => {
+    try {
+      const res = await fetch(`${API_URL}/api/audit/sum?page=${page}&per_page=10`, {
+        credentials: "include",
+      });
+      const data = await res.json();
+      setSumData(data);
+    } catch {
+      setSumData(null);
+    }
+  };
+
+  const handleLogout = async () => {
+    await logout();
+    router.push("/login");
+  };
+
+  const formatDate = (dateStr: string) => {
+    return new Date(dateStr).toLocaleString();
+  };
+
+  if (isLoading) {
+    return (
+      <main style={styles.main}>
+        <div style={styles.loader}>Loading...</div>
+      </main>
+    );
+  }
+
+  if (!user) {
+    return null;
+  }
+
+  return (
+    <main style={styles.main}>
+      <div style={styles.header}>
+        <div style={styles.nav}>
+          <a href="/" style={styles.navLink}>Counter</a>
+          <span style={styles.navDivider}>•</span>
+          <a href="/sum" style={styles.navLink}>Sum</a>
+          <span style={styles.navDivider}>•</span>
+          <span style={styles.navCurrent}>Audit</span>
+        </div>
+        <div style={styles.userInfo}>
+          <span style={styles.userEmail}>{user.email}</span>
+          <button onClick={handleLogout} style={styles.logoutBtn}>
+            Sign out
+          </button>
+        </div>
+      </div>
+
+      <div style={styles.content}>
+        <div style={styles.tablesContainer}>
+          {/* Counter Records Table */}
+          <div style={styles.tableCard}>
+            <div style={styles.tableHeader}>
+              <h2 style={styles.tableTitle}>Counter Activity</h2>
+              <span style={styles.totalCount}>
+                {counterData?.total ?? 0} records
+              </span>
+            </div>
+            <div style={styles.tableWrapper}>
+              <table style={styles.table}>
+                <thead>
+                  <tr>
+                    <th style={styles.th}>User</th>
+                    <th style={styles.th}>Before</th>
+                    <th style={styles.th}>After</th>
+                    <th style={styles.th}>Date</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {counterData?.records.map((record) => (
+                    <tr key={record.id} style={styles.tr}>
+                      <td style={styles.td}>{record.user_email}</td>
+                      <td style={styles.tdNum}>{record.value_before}</td>
+                      <td style={styles.tdNum}>{record.value_after}</td>
+                      <td style={styles.tdDate}>{formatDate(record.created_at)}</td>
+                    </tr>
+                  ))}
+                  {(!counterData || counterData.records.length === 0) && (
+                    <tr>
+                      <td colSpan={4} style={styles.emptyRow}>No records yet</td>
+                    </tr>
+                  )}
+                </tbody>
+              </table>
+            </div>
+            {counterData && counterData.total_pages > 1 && (
+              <div style={styles.pagination}>
+                <button
+                  onClick={() => setCounterPage((p) => Math.max(1, p - 1))}
+                  disabled={counterPage === 1}
+                  style={styles.pageBtn}
+                >
+                  ←
+                </button>
+                <span style={styles.pageInfo}>
+                  {counterPage} / {counterData.total_pages}
+                </span>
+                <button
+                  onClick={() => setCounterPage((p) => Math.min(counterData.total_pages, p + 1))}
+                  disabled={counterPage === counterData.total_pages}
+                  style={styles.pageBtn}
+                >
+                  →
+                </button>
+              </div>
+            )}
+          </div>
+
+          {/* Sum Records Table */}
+          <div style={styles.tableCard}>
+            <div style={styles.tableHeader}>
+              <h2 style={styles.tableTitle}>Sum Activity</h2>
+              <span style={styles.totalCount}>
+                {sumData?.total ?? 0} records
+              </span>
+            </div>
+            <div style={styles.tableWrapper}>
+              <table style={styles.table}>
+                <thead>
+                  <tr>
+                    <th style={styles.th}>User</th>
+                    <th style={styles.th}>A</th>
+                    <th style={styles.th}>B</th>
+                    <th style={styles.th}>Result</th>
+                    <th style={styles.th}>Date</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {sumData?.records.map((record) => (
+                    <tr key={record.id} style={styles.tr}>
+                      <td style={styles.td}>{record.user_email}</td>
+                      <td style={styles.tdNum}>{record.a}</td>
+                      <td style={styles.tdNum}>{record.b}</td>
+                      <td style={styles.tdResult}>{record.result}</td>
+                      <td style={styles.tdDate}>{formatDate(record.created_at)}</td>
+                    </tr>
+                  ))}
+                  {(!sumData || sumData.records.length === 0) && (
+                    <tr>
+                      <td colSpan={5} style={styles.emptyRow}>No records yet</td>
+                    </tr>
+                  )}
+                </tbody>
+              </table>
+            </div>
+            {sumData && sumData.total_pages > 1 && (
+              <div style={styles.pagination}>
+                <button
+                  onClick={() => setSumPage((p) => Math.max(1, p - 1))}
+                  disabled={sumPage === 1}
+                  style={styles.pageBtn}
+                >
+                  ←
+                </button>
+                <span style={styles.pageInfo}>
+                  {sumPage} / {sumData.total_pages}
+                </span>
+                <button
+                  onClick={() => setSumPage((p) => Math.min(sumData.total_pages, p + 1))}
+                  disabled={sumPage === sumData.total_pages}
+                  style={styles.pageBtn}
+                >
+                  →
+                </button>
+              </div>
+            )}
+          </div>
+        </div>
+      </div>
+    </main>
+  );
+}
+
+const styles: Record<string, React.CSSProperties> = {
+  main: {
+    minHeight: "100vh",
+    background: "linear-gradient(135deg, #0f0f23 0%, #1a1a3e 50%, #2d1b4e 100%)",
+    display: "flex",
+    flexDirection: "column",
+  },
+  loader: {
+    flex: 1,
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "center",
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.5)",
+    fontSize: "1.125rem",
+  },
+  header: {
+    padding: "1.5rem 2rem",
+    borderBottom: "1px solid rgba(255, 255, 255, 0.06)",
+    display: "flex",
+    justifyContent: "space-between",
+    alignItems: "center",
+  },
+  nav: {
+    display: "flex",
+    alignItems: "center",
+    gap: "0.75rem",
+  },
+  navLink: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.5)",
+    fontSize: "0.875rem",
+    textDecoration: "none",
+    transition: "color 0.2s",
+  },
+  navDivider: {
+    color: "rgba(255, 255, 255, 0.2)",
+    fontSize: "0.75rem",
+  },
+  navCurrent: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "#a78bfa",
+    fontSize: "0.875rem",
+    fontWeight: 600,
+  },
+  userInfo: {
+    display: "flex",
+    alignItems: "center",
+    gap: "1rem",
+  },
+  userEmail: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.6)",
+    fontSize: "0.875rem",
+  },
+  logoutBtn: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    padding: "0.5rem 1rem",
+    fontSize: "0.875rem",
+    fontWeight: 500,
+    background: "rgba(255, 255, 255, 0.05)",
+    color: "rgba(255, 255, 255, 0.7)",
+    border: "1px solid rgba(255, 255, 255, 0.1)",
+    borderRadius: "8px",
+    cursor: "pointer",
+    transition: "all 0.2s",
+  },
+  content: {
+    flex: 1,
+    padding: "2rem",
+    overflowY: "auto",
+  },
+  tablesContainer: {
+    display: "flex",
+    flexDirection: "column",
+    gap: "2rem",
+    maxWidth: "1200px",
+    margin: "0 auto",
+  },
+  tableCard: {
+    background: "rgba(255, 255, 255, 0.03)",
+    backdropFilter: "blur(10px)",
+    border: "1px solid rgba(255, 255, 255, 0.08)",
+    borderRadius: "20px",
+    padding: "1.5rem",
+    boxShadow: "0 25px 50px -12px rgba(0, 0, 0, 0.5)",
+  },
+  tableHeader: {
+    display: "flex",
+    justifyContent: "space-between",
+    alignItems: "center",
+    marginBottom: "1rem",
+  },
+  tableTitle: {
+    fontFamily: "'Instrument Serif', Georgia, serif",
+    fontSize: "1.5rem",
+    fontWeight: 400,
+    color: "#fff",
+    margin: 0,
+  },
+  totalCount: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    fontSize: "0.875rem",
+    color: "rgba(255, 255, 255, 0.4)",
+  },
+  tableWrapper: {
+    overflowX: "auto",
+  },
+  table: {
+    width: "100%",
+    borderCollapse: "collapse",
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+  },
+  th: {
+    textAlign: "left",
+    padding: "0.75rem 1rem",
+    fontSize: "0.75rem",
+    fontWeight: 600,
+    color: "rgba(255, 255, 255, 0.4)",
+    textTransform: "uppercase",
+    letterSpacing: "0.05em",
+    borderBottom: "1px solid rgba(255, 255, 255, 0.08)",
+  },
+  tr: {
+    borderBottom: "1px solid rgba(255, 255, 255, 0.04)",
+  },
+  td: {
+    padding: "0.875rem 1rem",
+    fontSize: "0.875rem",
+    color: "rgba(255, 255, 255, 0.7)",
+  },
+  tdNum: {
+    padding: "0.875rem 1rem",
+    fontSize: "0.875rem",
+    color: "rgba(255, 255, 255, 0.9)",
+    fontFamily: "'DM Sans', monospace",
+  },
+  tdResult: {
+    padding: "0.875rem 1rem",
+    fontSize: "0.875rem",
+    color: "#a78bfa",
+    fontWeight: 600,
+    fontFamily: "'DM Sans', monospace",
+  },
+  tdDate: {
+    padding: "0.875rem 1rem",
+    fontSize: "0.75rem",
+    color: "rgba(255, 255, 255, 0.4)",
+  },
+  emptyRow: {
+    padding: "2rem 1rem",
+    textAlign: "center",
+    color: "rgba(255, 255, 255, 0.3)",
+    fontSize: "0.875rem",
+  },
+  pagination: {
+    display: "flex",
+    justifyContent: "center",
+    alignItems: "center",
+    gap: "1rem",
+    marginTop: "1rem",
+    paddingTop: "1rem",
+    borderTop: "1px solid rgba(255, 255, 255, 0.06)",
+  },
+  pageBtn: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    padding: "0.5rem 1rem",
+    fontSize: "1rem",
+    background: "rgba(255, 255, 255, 0.05)",
+    color: "rgba(255, 255, 255, 0.7)",
+    border: "1px solid rgba(255, 255, 255, 0.1)",
+    borderRadius: "8px",
+    cursor: "pointer",
+    transition: "all 0.2s",
+  },
+  pageInfo: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    fontSize: "0.875rem",
+    color: "rgba(255, 255, 255, 0.5)",
+  },
+};
+
diff --git a/frontend/app/page.tsx b/frontend/app/page.tsx
index aff961b..a75465c 100644
--- a/frontend/app/page.tsx
+++ b/frontend/app/page.tsx
@@ -56,6 +56,13 @@ export default function Home() {
   return (
     <main style={styles.main}>
       <div style={styles.header}>
+        <div style={styles.nav}>
+          <span style={styles.navCurrent}>Counter</span>
+          <span style={styles.navDivider}>•</span>
+          <a href="/sum" style={styles.navLink}>Sum</a>
+          <span style={styles.navDivider}>•</span>
+          <a href="/audit" style={styles.navLink}>Audit</a>
+        </div>
         <div style={styles.userInfo}>
           <span style={styles.userEmail}>{user.email}</span>
           <button onClick={handleLogout} style={styles.logoutBtn}>
@@ -97,11 +104,35 @@ const styles: Record<string, React.CSSProperties> = {
   header: {
     padding: "1.5rem 2rem",
     borderBottom: "1px solid rgba(255, 255, 255, 0.06)",
+    display: "flex",
+    justifyContent: "space-between",
+    alignItems: "center",
+  },
+  nav: {
+    display: "flex",
+    alignItems: "center",
+    gap: "0.75rem",
+  },
+  navLink: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.5)",
+    fontSize: "0.875rem",
+    textDecoration: "none",
+    transition: "color 0.2s",
+  },
+  navDivider: {
+    color: "rgba(255, 255, 255, 0.2)",
+    fontSize: "0.75rem",
+  },
+  navCurrent: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "#a78bfa",
+    fontSize: "0.875rem",
+    fontWeight: 600,
   },
   userInfo: {
     display: "flex",
     alignItems: "center",
-    justifyContent: "flex-end",
     gap: "1rem",
   },
   userEmail: {
diff --git a/frontend/app/sum/page.tsx b/frontend/app/sum/page.tsx
new file mode 100644
index 0000000..5e418ea
--- /dev/null
+++ b/frontend/app/sum/page.tsx
@@ -0,0 +1,344 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { useRouter } from "next/navigation";
+import { useAuth } from "../auth-context";
+import { API_URL } from "../config";
+
+export default function SumPage() {
+  const [a, setA] = useState("");
+  const [b, setB] = useState("");
+  const [result, setResult] = useState<number | null>(null);
+  const [showResult, setShowResult] = useState(false);
+  const { user, isLoading, logout } = useAuth();
+  const router = useRouter();
+
+  useEffect(() => {
+    if (!isLoading && !user) {
+      router.push("/login");
+    }
+  }, [isLoading, user, router]);
+
+  const handleSum = async () => {
+    const numA = parseFloat(a) || 0;
+    const numB = parseFloat(b) || 0;
+    
+    try {
+      const res = await fetch(`${API_URL}/api/sum`, {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        credentials: "include",
+        body: JSON.stringify({ a: numA, b: numB }),
+      });
+      const data = await res.json();
+      setResult(data.result);
+      setShowResult(true);
+    } catch {
+      // Fallback to local calculation if API fails
+      setResult(numA + numB);
+      setShowResult(true);
+    }
+  };
+
+  const handleReset = () => {
+    setA("");
+    setB("");
+    setResult(null);
+    setShowResult(false);
+  };
+
+  const handleLogout = async () => {
+    await logout();
+    router.push("/login");
+  };
+
+  if (isLoading) {
+    return (
+      <main style={styles.main}>
+        <div style={styles.loader}>Loading...</div>
+      </main>
+    );
+  }
+
+  if (!user) {
+    return null;
+  }
+
+  return (
+    <main style={styles.main}>
+      <div style={styles.header}>
+        <div style={styles.nav}>
+          <a href="/" style={styles.navLink}>Counter</a>
+          <span style={styles.navDivider}>•</span>
+          <span style={styles.navCurrent}>Sum</span>
+          <span style={styles.navDivider}>•</span>
+          <a href="/audit" style={styles.navLink}>Audit</a>
+        </div>
+        <div style={styles.userInfo}>
+          <span style={styles.userEmail}>{user.email}</span>
+          <button onClick={handleLogout} style={styles.logoutBtn}>
+            Sign out
+          </button>
+        </div>
+      </div>
+
+      <div style={styles.content}>
+        <div style={styles.card}>
+          <span style={styles.label}>Sum Calculator</span>
+          
+          {!showResult ? (
+            <div style={styles.inputSection}>
+              <div style={styles.inputRow}>
+                <div style={styles.inputWrapper}>
+                  <input
+                    type="number"
+                    value={a}
+                    onChange={(e) => setA(e.target.value)}
+                    placeholder="0"
+                    style={styles.input}
+                    aria-label="First number"
+                  />
+                </div>
+                <span style={styles.operator}>+</span>
+                <div style={styles.inputWrapper}>
+                  <input
+                    type="number"
+                    value={b}
+                    onChange={(e) => setB(e.target.value)}
+                    placeholder="0"
+                    style={styles.input}
+                    aria-label="Second number"
+                  />
+                </div>
+              </div>
+              <button 
+                onClick={handleSum} 
+                style={styles.sumBtn}
+                disabled={a === "" && b === ""}
+              >
+                <span style={styles.equalsIcon}>=</span>
+                Calculate
+              </button>
+            </div>
+          ) : (
+            <div style={styles.resultSection}>
+              <div style={styles.equation}>
+                <span style={styles.equationNum}>{parseFloat(a) || 0}</span>
+                <span style={styles.equationOp}>+</span>
+                <span style={styles.equationNum}>{parseFloat(b) || 0}</span>
+                <span style={styles.equationOp}>=</span>
+              </div>
+              <h1 style={styles.result}>{result}</h1>
+              <button onClick={handleReset} style={styles.resetBtn}>
+                <span style={styles.resetIcon}>↺</span>
+                Try Again
+              </button>
+            </div>
+          )}
+        </div>
+      </div>
+    </main>
+  );
+}
+
+const styles: Record<string, React.CSSProperties> = {
+  main: {
+    minHeight: "100vh",
+    background: "linear-gradient(135deg, #0f0f23 0%, #1a1a3e 50%, #2d1b4e 100%)",
+    display: "flex",
+    flexDirection: "column",
+  },
+  loader: {
+    flex: 1,
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "center",
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.5)",
+    fontSize: "1.125rem",
+  },
+  header: {
+    padding: "1.5rem 2rem",
+    borderBottom: "1px solid rgba(255, 255, 255, 0.06)",
+    display: "flex",
+    justifyContent: "space-between",
+    alignItems: "center",
+  },
+  nav: {
+    display: "flex",
+    alignItems: "center",
+    gap: "0.75rem",
+  },
+  navLink: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.5)",
+    fontSize: "0.875rem",
+    textDecoration: "none",
+    transition: "color 0.2s",
+  },
+  navDivider: {
+    color: "rgba(255, 255, 255, 0.2)",
+    fontSize: "0.75rem",
+  },
+  navCurrent: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "#a78bfa",
+    fontSize: "0.875rem",
+    fontWeight: 600,
+  },
+  userInfo: {
+    display: "flex",
+    alignItems: "center",
+    gap: "1rem",
+  },
+  userEmail: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    color: "rgba(255, 255, 255, 0.6)",
+    fontSize: "0.875rem",
+  },
+  logoutBtn: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    padding: "0.5rem 1rem",
+    fontSize: "0.875rem",
+    fontWeight: 500,
+    background: "rgba(255, 255, 255, 0.05)",
+    color: "rgba(255, 255, 255, 0.7)",
+    border: "1px solid rgba(255, 255, 255, 0.1)",
+    borderRadius: "8px",
+    cursor: "pointer",
+    transition: "all 0.2s",
+  },
+  content: {
+    flex: 1,
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "center",
+    padding: "2rem",
+  },
+  card: {
+    background: "rgba(255, 255, 255, 0.03)",
+    backdropFilter: "blur(10px)",
+    border: "1px solid rgba(255, 255, 255, 0.08)",
+    borderRadius: "32px",
+    padding: "3rem 4rem",
+    textAlign: "center",
+    boxShadow: "0 25px 50px -12px rgba(0, 0, 0, 0.5)",
+    minWidth: "400px",
+  },
+  label: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    display: "block",
+    color: "rgba(255, 255, 255, 0.4)",
+    fontSize: "0.875rem",
+    textTransform: "uppercase",
+    letterSpacing: "0.1em",
+    marginBottom: "2rem",
+  },
+  inputSection: {
+    display: "flex",
+    flexDirection: "column",
+    alignItems: "center",
+    gap: "2rem",
+  },
+  inputRow: {
+    display: "flex",
+    alignItems: "center",
+    gap: "1rem",
+  },
+  inputWrapper: {
+    position: "relative",
+  },
+  input: {
+    fontFamily: "'Instrument Serif', Georgia, serif",
+    fontSize: "3rem",
+    fontWeight: 400,
+    width: "120px",
+    padding: "0.75rem 1rem",
+    textAlign: "center",
+    background: "rgba(255, 255, 255, 0.05)",
+    border: "2px solid rgba(255, 255, 255, 0.1)",
+    borderRadius: "16px",
+    color: "#fff",
+    outline: "none",
+    transition: "border-color 0.2s, box-shadow 0.2s",
+  },
+  operator: {
+    fontFamily: "'Instrument Serif', Georgia, serif",
+    fontSize: "3rem",
+    color: "#a78bfa",
+    fontWeight: 400,
+  },
+  sumBtn: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    padding: "1rem 2.5rem",
+    fontSize: "1.125rem",
+    fontWeight: 600,
+    background: "linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%)",
+    color: "#fff",
+    border: "none",
+    borderRadius: "16px",
+    cursor: "pointer",
+    display: "inline-flex",
+    alignItems: "center",
+    gap: "0.5rem",
+    transition: "transform 0.2s, box-shadow 0.2s",
+    boxShadow: "0 4px 14px rgba(99, 102, 241, 0.4)",
+  },
+  equalsIcon: {
+    fontSize: "1.5rem",
+    fontWeight: 400,
+  },
+  resultSection: {
+    display: "flex",
+    flexDirection: "column",
+    alignItems: "center",
+  },
+  equation: {
+    display: "flex",
+    alignItems: "center",
+    gap: "0.5rem",
+    marginBottom: "0.5rem",
+  },
+  equationNum: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    fontSize: "1.25rem",
+    color: "rgba(255, 255, 255, 0.6)",
+  },
+  equationOp: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    fontSize: "1.25rem",
+    color: "rgba(139, 92, 246, 0.8)",
+  },
+  result: {
+    fontFamily: "'Instrument Serif', Georgia, serif",
+    fontSize: "7rem",
+    fontWeight: 400,
+    color: "#fff",
+    margin: 0,
+    lineHeight: 1,
+    background: "linear-gradient(135deg, #fff 0%, #a78bfa 100%)",
+    WebkitBackgroundClip: "text",
+    WebkitTextFillColor: "transparent",
+    backgroundClip: "text",
+  },
+  resetBtn: {
+    fontFamily: "'DM Sans', system-ui, sans-serif",
+    marginTop: "2rem",
+    padding: "0.875rem 2rem",
+    fontSize: "1rem",
+    fontWeight: 500,
+    background: "rgba(255, 255, 255, 0.05)",
+    color: "rgba(255, 255, 255, 0.7)",
+    border: "1px solid rgba(255, 255, 255, 0.1)",
+    borderRadius: "12px",
+    cursor: "pointer",
+    display: "inline-flex",
+    alignItems: "center",
+    gap: "0.5rem",
+    transition: "all 0.2s",
+  },
+  resetIcon: {
+    fontSize: "1.25rem",
+  },
+};
+