diff --git a/app/(auth)/login/page.tsx b/app/(auth)/login/page.tsx
index d2c3226..288ef26 100644
--- a/app/(auth)/login/page.tsx
+++ b/app/(auth)/login/page.tsx
@@ -11,10 +11,11 @@ import DestructibleAlert from "@/components/DestructibleAlert";
 import { useAuth } from "@/context/AuthContext";
 import { LoginForm } from "@/types/auth";
 import { CircleAlert } from "lucide-react";
+import { useAuthStore } from "@/stores/authStore";
 
 const LoginPage = () => {
   const router = useRouter();
-  const { setToken } = useAuth();
+  const { setToken } = useAuthStore();
 
   const [form, setForm] = useState<LoginForm>({
     identifier: "",
@@ -88,7 +89,7 @@ const LoginPage = () => {
                   }
                 />
               </div>
-              {error && <DestructibleAlert text={error} extraStyles="" />}
+              {error && <DestructibleAlert text={error} />}
 
               <h1 className="flex justify-center items-center gap-2 bg-green-200 p-4 rounded-full">
                 <CircleAlert size={20} />
diff --git a/app/(auth)/register/page.tsx b/app/(auth)/register/page.tsx
index 2fb2245..d6a9f2a 100644
--- a/app/(auth)/register/page.tsx
+++ b/app/(auth)/register/page.tsx
@@ -11,6 +11,7 @@ import BackgroundWrapper from "@/components/BackgroundWrapper";
 import FormField from "@/components/FormField";
 import DestructibleAlert from "@/components/DestructibleAlert";
 import { RegisterForm } from "@/types/auth";
+import { useAuthStore } from "@/stores/authStore";
 
 interface ValidationErrorItem {
   type: string;
@@ -27,7 +28,7 @@ interface CustomError extends Error {
 }
 
 export default function RegisterPage() {
-  const { setToken } = useAuth();
+  const { setToken } = useAuthStore();
   const router = useRouter();
   const [form, setForm] = useState<RegisterForm>({
     full_name: "",
diff --git a/app/(tabs)/categories/mocks/page.tsx b/app/(tabs)/categories/mocks/page.tsx
index f0e3ce0..af8bf4f 100644
--- a/app/(tabs)/categories/mocks/page.tsx
+++ b/app/(tabs)/categories/mocks/page.tsx
@@ -8,6 +8,7 @@ import BackgroundWrapper from "@/components/BackgroundWrapper";
 import { API_URL, getToken } from "@/lib/auth";
 import { Loader, RefreshCw } from "lucide-react";
 import { useAuth } from "@/context/AuthContext";
+import { useAuthStore } from "@/stores/authStore";
 
 type Mock = {
   test_id: string;
@@ -22,7 +23,7 @@ type Mock = {
 
 export default function MockScreen() {
   const router = useRouter();
-  const { user } = useAuth();
+  const { user } = useAuthStore();
 
   const [mocks, setMocks] = useState<Mock[]>([]);
   const [errorMsg, setErrorMsg] = useState<string | null>(null);
diff --git a/app/(tabs)/categories/subjects/page.tsx b/app/(tabs)/categories/subjects/page.tsx
index 802b136..d974e76 100644
--- a/app/(tabs)/categories/subjects/page.tsx
+++ b/app/(tabs)/categories/subjects/page.tsx
@@ -10,6 +10,7 @@ import { API_URL, getToken } from "@/lib/auth";
 import { Loader, RefreshCw } from "lucide-react";
 import { useAuth } from "@/context/AuthContext";
 import { Question } from "@/types/exam";
+import { useAuthStore } from "@/stores/authStore";
 
 type Subject = {
   subject_id: string;
@@ -19,7 +20,7 @@ type Subject = {
 
 export default function PaperScreen() {
   const router = useRouter();
-  const { user } = useAuth();
+  const { user } = useAuthStore();
 
   const [subjects, setSubjects] = useState<Subject[]>([]);
   const [errorMsg, setErrorMsg] = useState<string | null>(null);
@@ -70,7 +71,7 @@ export default function PaperScreen() {
         <Header displayTabTitle="Subjects" />
         <div className="overflow-y-auto">
           <div className="mt-5 px-5">
-            <DestructibleAlert text={errorMsg} extraStyles="" />
+            <DestructibleAlert text={errorMsg} />
           </div>
           <div className="flex justify-center mt-4">
             <button
diff --git a/app/(tabs)/categories/topics/page.tsx b/app/(tabs)/categories/topics/page.tsx
index 7f3d909..04229f8 100644
--- a/app/(tabs)/categories/topics/page.tsx
+++ b/app/(tabs)/categories/topics/page.tsx
@@ -8,6 +8,7 @@ import BackgroundWrapper from "@/components/BackgroundWrapper";
 import { API_URL, getToken } from "@/lib/auth";
 import { Loader, RefreshCw } from "lucide-react";
 import { useAuth } from "@/context/AuthContext";
+import { useAuthStore } from "@/stores/authStore";
 
 type Topic = {
   topic_id: string;
@@ -21,7 +22,7 @@ type Topic = {
 
 export default function TopicScreen() {
   const router = useRouter();
-  const { user } = useAuth();
+  const { user } = useAuthStore();
 
   const [topics, setTopics] = useState<Topic[]>([]);
   const [errorMsg, setErrorMsg] = useState<string | null>(null);
@@ -72,7 +73,7 @@ export default function TopicScreen() {
         <Header displayTabTitle="Subjects" />
         <div className="overflow-y-auto">
           <div className="mt-5 px-5">
-            <DestructibleAlert text={errorMsg} extraStyles="" />
+            <DestructibleAlert text={errorMsg} />
           </div>
           <div className="flex justify-center mt-4">
             <button
diff --git a/app/(tabs)/settings/page.tsx b/app/(tabs)/settings/page.tsx
index 9b1d417..3e7f930 100644
--- a/app/(tabs)/settings/page.tsx
+++ b/app/(tabs)/settings/page.tsx
@@ -3,7 +3,7 @@
 import BackgroundWrapper from "@/components/BackgroundWrapper";
 import { Avatar, AvatarFallback } from "@/components/ui/avatar";
 import { useAuth } from "@/context/AuthContext";
-import { clearAuthToken } from "@/lib/auth";
+import { useAuthStore } from "@/stores/authStore";
 import {
   Bookmark,
   ChartColumn,
@@ -23,10 +23,10 @@ import React from "react";
 
 const SettingsPage = () => {
   const router = useRouter();
-  const { user, isLoading } = useAuth();
+  const { user, logout } = useAuthStore();
 
   function handleLogout() {
-    clearAuthToken();
+    logout();
     router.replace("/");
   }
 
diff --git a/app/exam/[id]/page.tsx b/app/exam/[id]/page.tsx
index 912f3ee..0845d04 100644
--- a/app/exam/[id]/page.tsx
+++ b/app/exam/[id]/page.tsx
@@ -1,14 +1,12 @@
 "use client";
 
-import React, { useEffect, useCallback, useMemo } from "react";
+import React, { useEffect, useCallback } from "react";
 import { useRouter, useSearchParams } from "next/navigation";
-import { useTimer } from "@/context/TimerContext";
-import { useExam } from "@/context/ExamContext";
 import Header from "@/components/Header";
-import { useModal } from "@/context/ModalContext";
-import Modal from "@/components/ExamModal";
 import QuestionItem from "@/components/QuestionItem";
 import BackgroundWrapper from "@/components/BackgroundWrapper";
+import { useExamStore } from "@/stores/examStore";
+import { useTimerStore } from "@/stores/timerStore";
 
 export default function ExamPage() {
   const router = useRouter();
@@ -16,21 +14,25 @@ export default function ExamPage() {
   const test_id = searchParams.get("test_id") || "";
   const type = searchParams.get("type") || "";
 
-  // const { isOpen, close, open } = useModal();
-  const { timeRemaining, setInitialTime, stopTimer } = useTimer();
   const { test, answers, startExam, setAnswer, submitExam, cancelExam } =
-    useExam();
+    useExamStore();
+  const { resetTimer, stopTimer } = useTimerStore();
 
-  // Start exam + timer
+  // Start exam + timer automatically
   useEffect(() => {
     if (type && test_id) {
-      startExam(type, test_id).then(() => {
-        if (test?.metadata.time_limit_minutes) {
-          setInitialTime(test.metadata.time_limit_minutes * 60); // convert to seconds
+      startExam(type, test_id).then((fetchedTest) => {
+        if (fetchedTest?.metadata.time_limit_minutes) {
+          resetTimer(fetchedTest.metadata.time_limit_minutes * 60, () => {
+            // Timer ended → auto-submit exam
+            submitExam(type);
+            router.push(`/categories/${type}s`);
+            alert("Time's up! Your exam has been submitted.");
+          });
         }
       });
     }
-  }, [type, test_id, startExam, setInitialTime]);
+  }, [type, test_id, startExam, resetTimer, submitExam, router]);
 
   const showExitDialog = useCallback(() => {
     if (window.confirm("Are you sure you want to quit the exam?")) {
@@ -38,7 +40,7 @@ export default function ExamPage() {
       cancelExam();
       router.push(`/categories/${type}s`);
     }
-  }, [stopTimer, cancelExam, router]);
+  }, [stopTimer, cancelExam, router, type]);
 
   if (!test) {
     return (
@@ -51,75 +53,16 @@ export default function ExamPage() {
     );
   }
 
-  // answered set for modal overview
-  // const answeredSet = useMemo(
-  //   () =>
-  //     new Set(
-  //       answers
-  //         .map((a, idx) =>
-  //           a !== null && a !== undefined ? idx.toString() : null
-  //         )
-  //         .filter(Boolean) as string[]
-  //     ),
-  //   [answers]
-  // );
+  const handleSubmitExam = (type: string) => {
+    submitExam(type);
+    router.push(`/categories/${type}s`);
+  };
 
   return (
     <div className="min-h-screen bg-gray-50">
       {/* Header with live timer */}
       <Header />
 
-      {/* Modal: Question overview */}
-      {/* <Modal open={isOpen} onClose={close} title="Exam Overview">
-        <div>
-          <div className="flex gap-6 mb-4">
-            <p className="font-medium">Questions: {test.questions.length}</p>
-            <p className="font-medium">
-              Answered:{" "}
-              <span className="text-blue-900 font-bold">
-                {answeredSet.size}
-              </span>
-            </p>
-            <p className="font-medium">
-              Skipped:{" "}
-              <span className="text-yellow-600 font-bold">
-                {test.questions.length - answeredSet.size}
-              </span>
-            </p>
-          </div>
-
-          <div className="h-[0.5px] border-[0.5px] border-black/10 w-full my-3"></div>
-
-          <section className="flex flex-wrap gap-4">
-            {test.questions.map((q, idx) => {
-              const answered = answeredSet.has(String(idx));
-              return (
-                <div
-                  key={q.question_id}
-                  className={`h-12 w-12 rounded-full flex items-center justify-center cursor-pointer
-                  ${
-                    answered
-                      ? "bg-blue-900 text-white"
-                      : "bg-gray-200 text-gray-900"
-                  }
-                  hover:opacity-80 transition`}
-                  onClick={() => {
-                    // optional: scroll to question
-                    const el = document.getElementById(`question-${idx}`);
-                    if (el) {
-                      el.scrollIntoView({ behavior: "smooth" });
-                      close();
-                    }
-                  }}
-                >
-                  {idx + 1}
-                </div>
-              );
-            })}
-          </section>
-        </div>
-      </Modal> */}
-
       {/* Questions */}
       <BackgroundWrapper>
         <div className="container mx-auto px-6 py-8 mb-20">
@@ -137,7 +80,7 @@ export default function ExamPage() {
           {/* Bottom submit bar */}
           <div className="fixed bottom-0 left-0 right-0 bg-white border-t border-gray-200 flex">
             <button
-              onClick={submitExam}
+              onClick={() => handleSubmitExam(type)}
               className="flex-1 bg-blue-900 text-white p-6 font-bold text-lg hover:bg-blue-800 transition-colors"
             >
               Submit
diff --git a/app/exam/pretest/page.tsx b/app/exam/pretest/page.tsx
index 3a96e7f..7614d6b 100644
--- a/app/exam/pretest/page.tsx
+++ b/app/exam/pretest/page.tsx
@@ -16,11 +16,12 @@ import { API_URL, getToken } from "@/lib/auth";
 import { useExam } from "@/context/ExamContext";
 import { Test } from "@/types/exam";
 import { Metadata } from "@/types/exam";
+import { useExamStore } from "@/stores/examStore";
 
 function PretestPageContent() {
   const router = useRouter();
   const searchParams = useSearchParams();
-  const { startExam } = useExam();
+  const { startExam } = useExamStore();
   const [examData, setExamData] = useState<Test>();
 
   // Get params from URL search params
diff --git a/app/layout.tsx b/app/layout.tsx
index 034753d..ec7a0e5 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -3,6 +3,7 @@ import { Montserrat } from "next/font/google";
 import "./globals.css";
 
 import { Providers } from "./providers";
+import AuthInitializer from "@/components/AuthInitializer";
 
 const montserrat = Montserrat({
   subsets: ["latin"],
@@ -24,7 +25,9 @@ export default function RootLayout({
   return (
     <html lang="en" className={montserrat.variable}>
       <body className="font-sans">
-        <Providers>{children}</Providers>
+        <AuthInitializer>
+          <Providers>{children}</Providers>
+        </AuthInitializer>
       </body>
     </html>
   );
diff --git a/app/providers.tsx b/app/providers.tsx
index 3a17280..e8c0bf1 100644
--- a/app/providers.tsx
+++ b/app/providers.tsx
@@ -6,13 +6,5 @@ import { AuthProvider } from "@/context/AuthContext";
 import { ModalProvider } from "@/context/ModalContext";
 
 export function Providers({ children }: { children: React.ReactNode }) {
-  return (
-    <TimerProvider>
-      <AuthProvider>
-        <ExamProvider>
-          <ModalProvider>{children}</ModalProvider>
-        </ExamProvider>
-      </AuthProvider>
-    </TimerProvider>
-  );
+  return <ModalProvider>{children}</ModalProvider>;
 }
diff --git a/components/AuthInitializer.tsx b/components/AuthInitializer.tsx
new file mode 100644
index 0000000..cfee7ab
--- /dev/null
+++ b/components/AuthInitializer.tsx
@@ -0,0 +1,40 @@
+"use client";
+
+import { useEffect } from "react";
+import { useAuthStore } from "@/stores/authStore";
+import { useRouter, usePathname } from "next/navigation";
+
+export default function AuthInitializer({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  const { initializeAuth, isLoading, token } = useAuthStore();
+  const router = useRouter();
+  const pathname = usePathname();
+
+  useEffect(() => {
+    const run = async () => {
+      await initializeAuth();
+
+      // Routing logic based on auth state
+      const publicPages = ["/", "/login", "/register"];
+
+      if (token) {
+        if (publicPages.includes(pathname)) {
+          router.replace("/home");
+        }
+      } else {
+        if (!publicPages.includes(pathname)) {
+          router.replace("/");
+        }
+      }
+    };
+
+    run();
+  }, [pathname, token, initializeAuth, router]);
+
+  if (isLoading) return <p>Loading...</p>;
+
+  return <>{children}</>;
+}
diff --git a/components/DestructibleAlert.tsx b/components/DestructibleAlert.tsx
index 29e1224..b6a4eb1 100644
--- a/components/DestructibleAlert.tsx
+++ b/components/DestructibleAlert.tsx
@@ -2,7 +2,7 @@ import React, { JSX } from "react";
 
 interface DestructibleAlertProps {
   text: string;
-  icon: JSX.Element;
+  icon?: JSX.Element;
 }
 
 const DestructibleAlert: React.FC<DestructibleAlertProps> = ({
diff --git a/components/Header.tsx b/components/Header.tsx
index 38c83e9..8719607 100644
--- a/components/Header.tsx
+++ b/components/Header.tsx
@@ -9,6 +9,9 @@ import { useExam } from "@/context/ExamContext";
 import { Avatar, AvatarFallback } from "@/components/ui/avatar";
 import { useModal } from "@/context/ModalContext";
 import { useAuth } from "@/context/AuthContext";
+import { useAuthStore } from "@/stores/authStore";
+import { useTimerStore } from "@/stores/timerStore";
+import { useExamStore } from "@/stores/examStore";
 
 interface HeaderProps {
   displayUser?: boolean;
@@ -23,9 +26,9 @@ const Header = ({
 }: HeaderProps) => {
   const router = useRouter();
   const { open } = useModal();
-  const { cancelExam } = useExam();
-  const { stopTimer, timeRemaining } = useTimer();
-  const { user } = useAuth();
+  const { cancelExam } = useExamStore();
+  const { stopTimer, timeRemaining } = useTimerStore();
+  const { user } = useAuthStore();
 
   const showExitDialog = () => {
     const confirmed = window.confirm("Are you sure you want to quit the exam?");
diff --git a/package-lock.json b/package-lock.json
index d6c2cb5..de35052 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -20,7 +20,8 @@
         "react": "^19.0.0",
         "react-dom": "^19.0.0",
         "tailwind-merge": "^3.3.1",
-        "uuid": "^11.1.0"
+        "uuid": "^11.1.0",
+        "zustand": "^5.0.8"
       },
       "devDependencies": {
         "@capacitor/cli": "^7.4.2",
@@ -7789,6 +7790,35 @@
       "funding": {
         "url": "https://github.com/sponsors/sindresorhus"
       }
+    },
+    "node_modules/zustand": {
+      "version": "5.0.8",
+      "resolved": "https://registry.npmjs.org/zustand/-/zustand-5.0.8.tgz",
+      "integrity": "sha512-gyPKpIaxY9XcO2vSMrLbiER7QMAMGOQZVRdJ6Zi782jkbzZygq5GI9nG8g+sMgitRtndwaBSl7uiqC49o1SSiw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=12.20.0"
+      },
+      "peerDependencies": {
+        "@types/react": ">=18.0.0",
+        "immer": ">=9.0.6",
+        "react": ">=18.0.0",
+        "use-sync-external-store": ">=1.2.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/react": {
+          "optional": true
+        },
+        "immer": {
+          "optional": true
+        },
+        "react": {
+          "optional": true
+        },
+        "use-sync-external-store": {
+          "optional": true
+        }
+      }
     }
   }
 }
diff --git a/package.json b/package.json
index 0a09848..ae945b1 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,8 @@
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "tailwind-merge": "^3.3.1",
-    "uuid": "^11.1.0"
+    "uuid": "^11.1.0",
+    "zustand": "^5.0.8"
   },
   "devDependencies": {
     "@capacitor/cli": "^7.4.2",
diff --git a/stores/authStore.ts b/stores/authStore.ts
new file mode 100644
index 0000000..4716c3a
--- /dev/null
+++ b/stores/authStore.ts
@@ -0,0 +1,90 @@
+"use client";
+
+import { create } from "zustand";
+import { UserData } from "@/types/auth";
+import { API_URL } from "@/lib/auth";
+
+// Cookie utilities
+const getCookie = (name: string): string | null => {
+  if (typeof document === "undefined") return null;
+
+  const value = `; ${document.cookie}`;
+  const parts = value.split(`; ${name}=`);
+  if (parts.length === 2) {
+    return parts.pop()?.split(";").shift() || null;
+  }
+  return null;
+};
+
+const setCookie = (
+  name: string,
+  value: string | null,
+  days: number = 7
+): void => {
+  if (typeof document === "undefined") return;
+
+  if (value === null) {
+    document.cookie = `${name}=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/; SameSite=Strict; Secure`;
+  } else {
+    const expires = new Date();
+    expires.setTime(expires.getTime() + days * 24 * 60 * 60 * 1000);
+    document.cookie = `${name}=${value}; expires=${expires.toUTCString()}; path=/; SameSite=Strict; Secure`;
+  }
+};
+
+interface AuthState {
+  token: string | null;
+  isLoading: boolean;
+  user: UserData | null;
+
+  setToken: (token: string | null) => void;
+  fetchUser: () => Promise<void>;
+  logout: () => void;
+  initializeAuth: () => Promise<void>;
+}
+
+export const useAuthStore = create<AuthState>((set, get) => ({
+  token: null,
+  isLoading: true,
+  user: null,
+
+  setToken: (newToken) => {
+    set({ token: newToken });
+    setCookie("authToken", newToken);
+  },
+
+  fetchUser: async () => {
+    const token = get().token;
+    if (!token) return;
+
+    try {
+      const res = await fetch(`${API_URL}/me/profile/`, {
+        headers: {
+          Authorization: `Bearer ${token}`,
+        },
+      });
+
+      if (!res.ok) throw new Error("Failed to fetch user info");
+
+      const data: UserData = await res.json();
+      set({ user: data });
+    } catch (err) {
+      console.error("Error fetching user:", err);
+      get().logout();
+    }
+  },
+
+  logout: () => {
+    set({ token: null, user: null });
+    setCookie("authToken", null);
+  },
+
+  initializeAuth: async () => {
+    const storedToken = getCookie("authToken");
+    if (storedToken) {
+      set({ token: storedToken });
+      await get().fetchUser();
+    }
+    set({ isLoading: false });
+  },
+}));
diff --git a/stores/examStore.ts b/stores/examStore.ts
new file mode 100644
index 0000000..e7bd362
--- /dev/null
+++ b/stores/examStore.ts
@@ -0,0 +1,90 @@
+"use client";
+
+import { create } from "zustand";
+import { Test, Answer } from "@/types/exam";
+import { API_URL, getToken } from "@/lib/auth";
+
+interface ExamState {
+  test: Test | null;
+  answers: Answer[];
+
+  startExam: (testType: string, testId: string) => Promise<void>;
+  setAnswer: (questionIndex: number, answer: Answer) => void;
+  submitExam: (testType: string) => Promise<void>;
+  cancelExam: () => void;
+}
+
+export const useExamStore = create<ExamState>((set, get) => ({
+  test: null,
+  answers: [],
+
+  // start exam
+  startExam: async (testType: string, testId: string) => {
+    try {
+      const token = await getToken();
+      const res = await fetch(`${API_URL}/tests/${testType}/${testId}`, {
+        method: "GET",
+        headers: {
+          Authorization: `Bearer ${token}`,
+        },
+      });
+
+      if (!res.ok) throw new Error(`Failed to fetch test: ${res.status}`);
+      const data: Test = await res.json();
+
+      set({
+        test: data,
+        answers: Array(data.questions.length).fill(null),
+      });
+    } catch (err) {
+      console.error("startExam error:", err);
+    }
+  },
+
+  // set an answer
+  setAnswer: (questionIndex: number, answer: Answer) => {
+    set((state) => {
+      const updated = [...state.answers];
+      updated[questionIndex] = answer;
+      return { answers: updated };
+    });
+  },
+
+  // submit exam
+  submitExam: async (testType: string) => {
+    const { test, answers } = get();
+    if (!test) return;
+
+    const token = await getToken();
+
+    try {
+      const { test_id, attempt_id } = test.metadata;
+      console.log(answers);
+      const res = await fetch(
+        `${API_URL}/tests/${testType}/${test_id}/${attempt_id}`,
+        {
+          method: "POST",
+          headers: {
+            "Content-Type": "application/json",
+            Authorization: `Bearer ${token}`,
+          },
+          body: JSON.stringify({ answers }),
+        }
+      );
+
+      console.log(res);
+
+      if (!res.ok) throw new Error("Failed to submit exam");
+
+      // reset store
+      set({ test: null, answers: [] });
+    } catch (err) {
+      console.error("Failed to submit exam. Reason:", err);
+    }
+  },
+
+  // cancel exam
+  cancelExam: () => {
+    set({ test: null, answers: [] });
+  },
+}));
diff --git a/stores/timerStore.ts b/stores/timerStore.ts
new file mode 100644
index 0000000..c9194e4
--- /dev/null
+++ b/stores/timerStore.ts
@@ -0,0 +1,48 @@
+"use client";
+
+import { create } from "zustand";
+
+interface TimerState {
+  timeRemaining: number;
+  timerRef: NodeJS.Timeout | null;
+
+  resetTimer: (duration: number, onComplete?: () => void) => void;
+  stopTimer: () => void;
+  setInitialTime: (duration: number) => void;
+}
+
+export const useTimerStore = create<TimerState>((set, get) => ({
+  timeRemaining: 0,
+  timerRef: null,
+
+  resetTimer: (duration, onComplete) => {
+    const { timerRef } = get();
+
+    if (timerRef) clearInterval(timerRef);
+
+    const newRef = setInterval(() => {
+      set((state) => {
+        if (state.timeRemaining <= 1) {
+          clearInterval(newRef);
+          if (onComplete) onComplete(); // ✅ call callback when timer ends
+          return { timeRemaining: 0, timerRef: null };
+        }
+        return { timeRemaining: state.timeRemaining - 1 };
+      });
+    }, 1000);
+
+    set({ timeRemaining: duration, timerRef: newRef });
+  },
+
+  stopTimer: () => {
+    const { timerRef } = get();
+    if (timerRef) clearInterval(timerRef);
+    set({ timeRemaining: 0, timerRef: null });
+  },
+
+  setInitialTime: (duration) => {
+    const { timerRef } = get();
+    if (timerRef) clearInterval(timerRef);
+    set({ timeRemaining: duration, timerRef: null });
+  },
+}));