apps/api/src/routes/profile.ts

@@ -44,6 +44,8 @@ const parseProfileSettings = (raw: unknown): ProfileSettings => {
     ? (parsedNumberFormat as ProfileSettings["numberFormat"])
     : "suffix";
   return {
+    enableNotifications: rawObject.enableNotifications === true,
+    enableSounds: rawObject.enableSounds === true,
     numberFormat: numberFormat,
     showAchievementsUnlocked: rawObject.showAchievementsUnlocked !== false,
     showAdventurersRecruited: rawObject.showAdventurersRecruited !== false,
@@ -203,6 +205,8 @@ profileRouter.put("/", authMiddleware, async(context) => {
     ? (parsedNumberFormat as ProfileSettings["numberFormat"])
     : "suffix";
   const profileSettings: ProfileSettings = {
+    enableNotifications: body.profileSettings.enableNotifications ?? false,
+    enableSounds: body.profileSettings.enableSounds ?? false,
     numberFormat: numberFormat,
     showAchievementsUnlocked: body.profileSettings.showAchievementsUnlocked ?? true,
     showAdventurersRecruited: body.profileSettings.showAdventurersRecruited ?? true,

apps/web/src/components/game/aboutPanel.tsx

@@ -245,6 +245,17 @@ const howToPlay = [
       + " progress is permanent and survives all resets.",
     title: "📖 Story",
   },
+  {
+    body:
+      "Enable sound effects and browser notifications in your profile settings"
+      + " (click your character name in the top bar). Sound effects play when"
+      + " you defeat a boss, complete or fail a quest, unlock an achievement,"
+      + " prestige, transcend, or achieve apotheosis. Browser notifications"
+      + " alert you to the same events even when the game tab is in the"
+      + " background. You will be prompted to grant notification permission"
+      + " when you first enable them.",
+    title: "🔔 Sounds & Notifications",
+  },
 ];
 
 const formatDate = (dateString: string): string => {

apps/web/src/components/game/editProfileModal.tsx

@@ -16,6 +16,9 @@ import {
 import { type ChangeEvent, type JSX, useEffect, useState } from "react";
 import { updateProfile } from "../../api/client.js";
 import { useGame } from "../../context/gameContext.js";
+import {
+  requestNotificationPermission,
+} from "../../utils/notification.js";
 
 interface EditProfileModalProperties {
   readonly onClose: ()=> void;
@@ -96,6 +99,8 @@ const EditProfileModal = ({
     state,
     numberFormat: currentNumberFormat,
     setNumberFormat,
+    setEnableSounds,
+    setEnableNotifications,
   } = useGame();
   const player = state?.player;
 
@@ -157,6 +162,8 @@ const EditProfileModal = ({
         profileSettings,
       });
       setNumberFormat(profileSettings.numberFormat);
+      setEnableSounds(profileSettings.enableSounds);
+      setEnableNotifications(profileSettings.enableNotifications);
       setSaved(true);
       setTimeout(onClose, 900);
     } catch (error_: unknown) {
@@ -194,6 +201,30 @@ const EditProfileModal = ({
     setBio(event.target.value);
   }
 
+  function handleSoundsToggle(): void {
+    toggleSetting("enableSounds");
+  }
+
+  async function handleNotificationsEnable(): Promise<void> {
+    if (profileSettings.enableNotifications) {
+      toggleSetting("enableNotifications");
+      return;
+    }
+    const granted = await requestNotificationPermission();
+    if (granted) {
+      toggleSetting("enableNotifications");
+    } else {
+      setError(
+        "Browser notification permission was denied."
+        + " Please enable it in your browser settings.",
+      );
+    }
+  }
+
+  function handleNotificationsToggle(): void {
+    void handleNotificationsEnable();
+  }
+
   const isSaveDisabled = saving || characterName.trim() === "";
 
   let saveLabel = "Save Profile";
@@ -348,6 +379,46 @@ const EditProfileModal = ({
               </button>
             </div>
 
+            <div className="edit-profile-section">
+              <p className="edit-profile-label">{"Sounds & Notifications"}</p>
+              <p className="edit-profile-sublabel">
+                {"Control in-game sound effects and browser notifications."}
+              </p>
+              <button
+                className={`stat-toggle-btn ${
+                  profileSettings.enableSounds
+                    ? "stat-toggle-on"
+                    : "stat-toggle-off"
+                }`}
+                onClick={handleSoundsToggle}
+                type="button"
+              >
+                <span>{"🔊 Sound Effects"}</span>
+                <span className="stat-toggle-indicator">
+                  {profileSettings.enableSounds
+                    ? "✓ On"
+                    : "Off"}
+                </span>
+              </button>
+              <button
+                className={`stat-toggle-btn ${
+                  profileSettings.enableNotifications
+                    ? "stat-toggle-on"
+                    : "stat-toggle-off"
+                }`}
+                onClick={handleNotificationsToggle}
+                type="button"
+              >
+                <span>{"🔔 Browser Notifications"}</span>
+                <span className="stat-toggle-indicator">
+                  {profileSettings.enableNotifications
+                    ? "✓ On"
+                    : "Off"
+                  }
+                </span>
+              </button>
+            </div>
+
             <div className="edit-profile-section">
               <p className="edit-profile-label">{"Number Format"}</p>
               <p className="edit-profile-sublabel">

apps/web/src/components/game/prestigePanel.tsx

@@ -15,6 +15,8 @@ import {
   PRESTIGE_UPGRADES,
   PRESTIGE_UPGRADE_CATEGORY_LABELS,
 } from "../../data/prestigeUpgrades.js";
+import { sendNotification } from "../../utils/notification.js";
+import { playSound } from "../../utils/sound.js";
 import type { PrestigeUpgradeCategory } from "@elysium/types";
 
 const baseThreshold = 1_000_000;
@@ -84,6 +86,8 @@ const PrestigePanel = (): JSX.Element => {
     reload,
     formatNumber,
     buyPrestigeUpgrade,
+    enableNotifications,
+    enableSounds,
     toggleAutoPrestige,
   } = useGame();
   const [ isPending, setIsPending ] = useState(false);
@@ -124,6 +128,15 @@ const PrestigePanel = (): JSX.Element => {
         milestoneRunestones: data.milestoneRunestones,
         runestones:          data.runestones,
       });
+      if (enableSounds) {
+        playSound("prestige");
+      }
+      if (enableNotifications) {
+        sendNotification(
+          "⭐ Prestige!",
+          `You've reached prestige level ${data.newPrestigeCount.toString()}!`,
+        );
+      }
       await reload();
     } catch (error_: unknown) {
       setPrestigeError(

apps/web/src/context/gameContext.tsx

@@ -58,6 +58,8 @@ import {
 } from "../engine/tick.js";
 import { updateChallengeProgress } from "../utils/dailyChallenges.js";
 import { formatNumber as formatNumberUtil } from "../utils/format.js";
+import { sendNotification } from "../utils/notification.js";
+import { playSound } from "../utils/sound.js";
 
 const autoSaveIntervalMs = 30_000;
 const autoPrestigeThresholdBase = 1_000_000;
@@ -342,6 +344,26 @@ interface GameContextValue {
    */
   setNumberFormat: (format: NumberFormat)=> void;
 
+  /**
+   * Whether in-game sound effects are enabled.
+   */
+  enableSounds: boolean;
+
+  /**
+   * Whether browser system notifications are enabled.
+   */
+  enableNotifications: boolean;
+
+  /**
+   * Update the enable-sounds preference.
+   */
+  setEnableSounds: (enabled: boolean)=> void;
+
+  /**
+   * Update the enable-notifications preference.
+   */
+  setEnableNotifications: (enabled: boolean)=> void;
+
   /**
    * Format a number using the player's chosen notation style.
    */
@@ -499,11 +521,17 @@ export const GameProvider = ({
     null,
   );
   const [ numberFormat, setNumberFormat ] = useState<NumberFormat>("suffix");
+  const [ enableSounds, setEnableSounds ] = useState(false);
+  const [ enableNotifications, setEnableNotifications ] = useState(false);
+  const enableSoundsReference = useRef(false);
+  const enableNotificationsReference = useRef(false);
   const stateReference = useRef<GameState | null>(null);
   const lastSaveReference = useRef<number>(Date.now());
   const isSyncingReference = useRef(false);
   const rafReference = useRef<number | null>(null);
   const unlockedAchievementsReference = useRef<Array<Achievement>>([]);
+  const newlyCompletedQuestsCountReference = useRef(0);
+  const newlyFailedQuestsCountReference = useRef(0);
   const signatureReference = useRef<string | null>(
     localStorage.getItem("elysium_save_signature"),
   );
@@ -561,7 +589,11 @@ export const GameProvider = ({
           }
           // eslint-disable-next-line @typescript-eslint/consistent-type-assertions -- API response cast
           const profile = (await response.json()) as {
-            profileSettings?: { numberFormat?: NumberFormat };
+            profileSettings?: {
+              enableNotifications?: boolean;
+              enableSounds?:        boolean;
+              numberFormat?:        NumberFormat;
+            };
           };
           const fmt = profile.profileSettings?.numberFormat;
           if (
@@ -571,10 +603,14 @@ export const GameProvider = ({
           ) {
             setNumberFormat(fmt);
           }
+          setEnableSounds(profile.profileSettings?.enableSounds === true);
+          setEnableNotifications(
+            profile.profileSettings?.enableNotifications === true,
+          );
         }).
         catch(() => {
 
-          /* Fall back to default "suffix" */
+          /* Fall back to defaults */
         });
     } catch (error_: unknown) {
       setError(
@@ -589,6 +625,14 @@ export const GameProvider = ({
 
   reloadReference.current = reload;
 
+  useEffect(() => {
+    enableSoundsReference.current = enableSounds;
+  }, [ enableSounds ]);
+
+  useEffect(() => {
+    enableNotificationsReference.current = enableNotifications;
+  }, [ enableNotifications ]);
+
   useEffect(() => {
     void reload();
   }, [ reload ]);
@@ -904,6 +948,27 @@ export const GameProvider = ({
           },
         );
 
+        // Detect newly completed quests
+        newlyCompletedQuestsCountReference.current = next.quests.filter(
+          (q, index) => {
+            return (
+              previous.quests[index]?.status === "active"
+              && q.status === "completed"
+            );
+          },
+        ).length;
+
+        // Detect newly failed quests
+        newlyFailedQuestsCountReference.current = next.quests.filter(
+          (q, index) => {
+            const previousFailedAt = previous.quests[index]?.lastFailedAt;
+            return (
+              q.lastFailedAt !== undefined
+              && q.lastFailedAt !== previousFailedAt
+            );
+          },
+        ).length;
+
         return next;
       });
 
@@ -911,9 +976,37 @@ export const GameProvider = ({
         setUnlockedAchievements((previous) => {
           return [ ...previous, ...unlockedAchievementsReference.current ];
         });
+        if (enableSoundsReference.current) {
+          playSound("achievement");
+        }
+        if (enableNotificationsReference.current) {
+          for (const achievement of unlockedAchievementsReference.current) {
+            sendNotification("🏆 Achievement Unlocked!", achievement.name);
+          }
+        }
         unlockedAchievementsReference.current = [];
       }
 
+      if (newlyCompletedQuestsCountReference.current > 0) {
+        if (enableSoundsReference.current) {
+          playSound("questCompleted");
+        }
+        if (enableNotificationsReference.current) {
+          sendNotification("📜 Quest Complete!", "A quest has been completed.");
+        }
+        newlyCompletedQuestsCountReference.current = 0;
+      }
+
+      if (newlyFailedQuestsCountReference.current > 0) {
+        if (enableSoundsReference.current) {
+          playSound("questFailed");
+        }
+        if (enableNotificationsReference.current) {
+          sendNotification("💀 Quest Failed!", "A quest has failed.");
+        }
+        newlyFailedQuestsCountReference.current = 0;
+      }
+
       // Auto-save every 30 seconds (skip if a force sync is in-flight to avoid signature collisions)
       if (Date.now() - lastSaveReference.current >= autoSaveIntervalMs) {
         lastSaveReference.current = Date.now();
@@ -961,6 +1054,12 @@ export const GameProvider = ({
         isAutoPrestigingReference.current = true;
         void prestigeApi({}).
           then(async() => {
+            if (enableSoundsReference.current) {
+              playSound("prestige");
+            }
+            if (enableNotificationsReference.current) {
+              sendNotification("⭐ Prestige!", "You have ascended!");
+            }
             await reloadReference.current();
           }).
           catch(() => {
@@ -1004,6 +1103,17 @@ export const GameProvider = ({
                 return applyBossResult(previous, bossId, result);
               });
               setBattleResult({ bossName, result });
+              if (result.won) {
+                if (enableSoundsReference.current) {
+                  playSound("bossVictory");
+                }
+                if (enableNotificationsReference.current) {
+                  sendNotification(
+                    "⚔️ Boss Defeated!",
+                    `You defeated ${bossName}!`,
+                  );
+                }
+              }
             }).
             catch(() => {
 
@@ -1333,12 +1443,24 @@ export const GameProvider = ({
 
   const transcend = useCallback(async() => {
     const result = await transcendApi({});
+    if (enableSoundsReference.current) {
+      playSound("transcendence");
+    }
+    if (enableNotificationsReference.current) {
+      sendNotification("🌌 Transcendence!", "You have transcended reality!");
+    }
     await reload();
     return result;
   }, [ reload ]);
 
   const apotheosis = useCallback(async() => {
     const result = await achieveApotheosisApi({});
+    if (enableSoundsReference.current) {
+      playSound("apotheosis");
+    }
+    if (enableNotificationsReference.current) {
+      sendNotification("✨ Apotheosis!", "You have achieved godhood!");
+    }
     await reload();
     return result;
   }, [ reload ]);
@@ -1589,6 +1711,14 @@ export const GameProvider = ({
         return applyBossResult(previous, bossId, result);
       });
       setBattleResult({ bossName: boss.name, result: result });
+      if (result.won) {
+        if (enableSoundsReference.current) {
+          playSound("bossVictory");
+        }
+        if (enableNotificationsReference.current) {
+          sendNotification("⚔️ Boss Defeated!", `You defeated ${boss.name}!`);
+        }
+      }
     } catch {
       // Silently ignore — server errors shouldn't crash the UI
     }
@@ -1707,6 +1837,8 @@ export const GameProvider = ({
       dismissLoginBonus,
       dismissOfflineGold,
       dismissStoryChapter,
+      enableNotifications,
+      enableSounds,
       equipItem,
       error,
       forceSync,
@@ -1725,6 +1857,8 @@ export const GameProvider = ({
       saveSchemaVersion,
       schemaOutdated,
       setActiveCompanion,
+      setEnableNotifications,
+      setEnableSounds,
       setNumberFormat,
       startExploration,
       startQuest,
@@ -1758,6 +1892,8 @@ export const GameProvider = ({
     dismissLoginBonus,
     dismissOfflineGold,
     dismissStoryChapter,
+    enableNotifications,
+    enableSounds,
     equipItem,
     error,
     forceSync,
@@ -1775,6 +1911,8 @@ export const GameProvider = ({
     saveSchemaVersion,
     schemaOutdated,
     setActiveCompanion,
+    setEnableNotifications,
+    setEnableSounds,
     setNumberFormat,
     startExploration,
     startQuest,

apps/web/src/utils/notification.ts

@@ -0,0 +1,46 @@
+/**
+ * @file Browser notification utilities.
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+/**
+ * Requests browser notification permission from the user.
+ * @returns Whether permission was granted.
+ */
+const requestNotificationPermission = async(): Promise<boolean> => {
+  if (typeof Notification === "undefined") {
+    return false;
+  }
+  if (Notification.permission === "granted") {
+    return true;
+  }
+  if (Notification.permission === "denied") {
+    return false;
+  }
+  const permission = await Notification.requestPermission();
+  return permission === "granted";
+};
+
+/**
+ * Sends a browser notification if permission has been granted.
+ * @param title - The notification title text.
+ * @param body - The notification message displayed below the title.
+ */
+const sendNotification = (title: string, body: string): void => {
+  if (
+    typeof Notification === "undefined"
+    || Notification.permission !== "granted"
+  ) {
+    return;
+  }
+  try {
+    // eslint-disable-next-line no-new -- Notification constructor has side effects
+    new Notification(title, { body: body, icon: "/favicon.ico" });
+  } catch {
+    // Silently ignore — notifications may fail silently
+  }
+};
+
+export { requestNotificationPermission, sendNotification };

apps/web/src/utils/sound.ts

@@ -0,0 +1,110 @@
+/**
+ * @file Sound effect utilities using the Web Audio API.
+ * @copyright nhcarrigan
+ * @license Naomi's Public License
+ * @author Naomi Carrigan
+ */
+
+type SoundEvent =
+  | "achievement"
+  | "apotheosis"
+  | "bossVictory"
+  | "prestige"
+  | "questCompleted"
+  | "questFailed"
+  | "transcendence";
+
+interface SoundPattern {
+  frequencies:  Array<number>;
+  gain:         number;
+  noteDuration: number;
+  type:         OscillatorType;
+}
+
+// eslint-disable-next-line @typescript-eslint/naming-convention -- intentional constant name
+const SOUND_PATTERNS: Record<SoundEvent, SoundPattern> = {
+  achievement: {
+    frequencies:  [ 523, 659, 784, 1047 ],
+    gain:         0.3,
+    noteDuration: 0.12,
+    type:         "triangle",
+  },
+  apotheosis: {
+    frequencies:  [ 1047, 880, 784, 659, 523 ],
+    gain:         0.35,
+    noteDuration: 0.25,
+    type:         "sine",
+  },
+  bossVictory: {
+    frequencies:  [ 523, 784, 1047 ],
+    gain:         0.4,
+    noteDuration: 0.18,
+    type:         "square",
+  },
+  prestige: {
+    frequencies:  [ 392, 523, 659, 784 ],
+    gain:         0.35,
+    noteDuration: 0.15,
+    type:         "sawtooth",
+  },
+  questCompleted: {
+    frequencies:  [ 523, 659 ],
+    gain:         0.25,
+    noteDuration: 0.15,
+    type:         "sine",
+  },
+  questFailed: {
+    frequencies:  [ 392, 330, 261 ],
+    gain:         0.25,
+    noteDuration: 0.18,
+    type:         "triangle",
+  },
+  transcendence: {
+    frequencies:  [ 261, 329, 392, 523 ],
+    gain:         0.3,
+    noteDuration: 0.3,
+    type:         "sine",
+  },
+};
+
+// eslint-disable-next-line @typescript-eslint/init-declarations -- lazily initialised on first use
+let audioContext: AudioContext | undefined;
+
+const getAudioContext = (): AudioContext => {
+  if (audioContext === undefined) {
+    audioContext = new AudioContext();
+  }
+  return audioContext;
+};
+
+/**
+ * Plays a sound effect for a given game event using the Web Audio API.
+ * @param event - The game event to play a sound for.
+ */
+const playSound = (event: SoundEvent): void => {
+  try {
+    const context = getAudioContext();
+    const pattern = SOUND_PATTERNS[event];
+    for (const [ index, frequency ] of pattern.frequencies.entries()) {
+      const oscillator = context.createOscillator();
+      const gainNode = context.createGain();
+      oscillator.connect(gainNode);
+      gainNode.connect(context.destination);
+      oscillator.type = pattern.type;
+      oscillator.frequency.value = frequency;
+      const noteOffset = index * pattern.noteDuration;
+      const startTime = context.currentTime + noteOffset;
+      const endTime = startTime + pattern.noteDuration;
+      gainNode.gain.setValueAtTime(0, startTime);
+      gainNode.gain.linearRampToValueAtTime(pattern.gain, startTime + 0.01);
+      gainNode.gain.linearRampToValueAtTime(0, endTime);
+      oscillator.start(startTime);
+      oscillator.stop(endTime);
+    }
+  } catch {
+    // Silently ignore — audio may not be available in all environments
+  }
+};
+
+export type { SoundEvent };
+export { playSound };

packages/types/src/interfaces/profileSettings.ts

@@ -38,10 +38,22 @@ interface ProfileSettings {
    * Whether this player appears on the public leaderboards.
    */
   showOnLeaderboards: boolean;
+
+  /**
+   * Whether in-game sound effects are enabled.
+   */
+  enableSounds: boolean;
+
+  /**
+   * Whether browser system notifications are enabled.
+   */
+  enableNotifications: boolean;
 }
 
 // eslint-disable-next-line @typescript-eslint/naming-convention -- intentional constant name
 const DEFAULT_PROFILE_SETTINGS: ProfileSettings = {
+  enableNotifications:              false,
+  enableSounds:                     false,
   numberFormat:                     "suffix",
   showAchievementsUnlocked:         true,
   showAdventurersRecruited:         true,

packages/types/test/profileSettings.spec.ts

@@ -20,6 +20,8 @@ describe("DEFAULT_PROFILE_SETTINGS", () => {
     expect(DEFAULT_PROFILE_SETTINGS.showAdventurersRecruited).toBe(true);
     expect(DEFAULT_PROFILE_SETTINGS.showAchievementsUnlocked).toBe(true);
     expect(DEFAULT_PROFILE_SETTINGS.showOnLeaderboards).toBe(true);
+    expect(DEFAULT_PROFILE_SETTINGS.enableSounds).toBe(false);
+    expect(DEFAULT_PROFILE_SETTINGS.enableNotifications).toBe(false);
   });
 
   it("defaults numberFormat to suffix", () => {