diff --git a/src/App.svelte b/src/App.svelte
index df5b9e7..402d02c 100644
--- a/src/App.svelte
+++ b/src/App.svelte
@@ -1,6 +1,9 @@
 <script>
+    import { onMount } from 'svelte';
     import { fade } from 'svelte/transition';
+    import { getText } from './lib/localization.js';
     import { initLanguage } from './lib/localization.js';
+    import { loadProgress, acknowledgeMigration, isMigrationAcknowledged } from './lib/progress.js';
     import MainMenu from './scenes/MainMenu.svelte';
     import StoryIntro from './scenes/StoryIntro.svelte';
     import LevelIntro from './scenes/LevelIntro.svelte';
@@ -16,10 +19,25 @@
     let currentScene = $state('MainMenu');
     let sceneData = $state({});
 
+    // Migration modal — shown once on first v2 boot if legacy save was detected
+    let showMigrationModal = $state(false);
+
     function navigate(scene, data = {}) {
         sceneData = data;
         currentScene = scene;
     }
+
+    onMount(() => {
+        const { needsMigrationModal } = loadProgress();
+        if (needsMigrationModal && !isMigrationAcknowledged()) {
+            showMigrationModal = true;
+        }
+    });
+
+    function dismissMigration() {
+        showMigrationModal = false;
+        acknowledgeMigration();
+    }
 </script>
 
 <div class="game-container">
@@ -30,13 +48,13 @@
             {:else if currentScene === 'StoryIntro'}
                 <StoryIntro {navigate} />
             {:else if currentScene === 'LevelIntro'}
-                <LevelIntro {navigate} level={sceneData.level} lives={sceneData.lives} />
+                <LevelIntro {navigate} level={sceneData.level} />
             {:else if currentScene === 'LevelSelect'}
                 <LevelSelect {navigate} />
             {:else if currentScene === 'Game'}
-                <Game {navigate} level={sceneData.level} lives={sceneData.lives} />
+                <Game {navigate} level={sceneData.level} />
             {:else if currentScene === 'GameOver'}
-                <GameOver {navigate} level={sceneData.level} isLastLevel={sceneData.isLastLevel} />
+                <GameOver {navigate} level={sceneData.level} flow={sceneData.flow} />
             {:else if currentScene === 'Settings'}
                 <Settings {navigate} />
             {:else if currentScene === 'Guide'}
@@ -44,6 +62,17 @@
             {/if}
         </div>
     {/key}
+
+    {#if showMigrationModal}
+        <!-- svelte-ignore a11y_click_events_have_key_events -->
+        <div class="modal-backdrop" role="presentation" onclick={dismissMigration}>
+            <div class="modal" role="dialog" aria-modal="true" aria-labelledby="migration-title">
+                <h2 id="migration-title">{getText('migration.title')}</h2>
+                <p>{getText('migration.body')}</p>
+                <button class="modal-btn" onclick={dismissMigration}>{getText('migration.dismiss')}</button>
+            </div>
+        </div>
+    {/if}
 </div>
 
 <style>
@@ -58,4 +87,47 @@
         position: absolute;
         inset: 0;
     }
+    .modal-backdrop {
+        position: absolute;
+        inset: 0;
+        background: rgba(0, 0, 0, 0.72);
+        display: flex;
+        align-items: center;
+        justify-content: center;
+        z-index: 100;
+    }
+    .modal {
+        background: var(--bg-dark, #0a0a1a);
+        border: 2px solid var(--btn-border, #334);
+        border-radius: 8px;
+        padding: 32px 40px;
+        max-width: 420px;
+        width: 90%;
+        display: flex;
+        flex-direction: column;
+        align-items: center;
+        gap: 16px;
+        text-align: center;
+    }
+    .modal h2 {
+        font: var(--font-title, bold 28px Arial, sans-serif);
+        color: var(--text-accent, #44ffaa);
+    }
+    .modal p {
+        font: var(--font-body, 16px Arial, sans-serif);
+        color: var(--text-primary, #ccccdd);
+        line-height: 1.5;
+    }
+    .modal-btn {
+        margin-top: 8px;
+        padding: 10px 32px;
+        font: var(--font-button, bold 14px Arial, sans-serif);
+        background: var(--btn-default, #1a1a2e);
+        color: var(--text-primary, #ccccdd);
+        border: 2px solid var(--btn-border, #334);
+        border-radius: 4px;
+        cursor: pointer;
+        transition: background 0.15s;
+    }
+    .modal-btn:hover { background: var(--btn-hover, #252540); }
 </style>
diff --git a/src/lib/progress.js b/src/lib/progress.js
index 68ce494..3351abd 100644
--- a/src/lib/progress.js
+++ b/src/lib/progress.js
@@ -1,6 +1,7 @@
 // Level progress persistence via localStorage
 
 const STORAGE_KEY = 'nntv-progress';
+const MIGRATION_KEY = 'nntv-migration-v2';
 
 const DEFAULT_PROGRESS = {
     maxLevel: 1,
@@ -9,22 +10,63 @@ const DEFAULT_PROGRESS = {
     levelBestMoves: {},
 };
 
-export function getProgress() {
+/**
+ * Returns { progress, needsMigrationModal }.
+ * If saved data has legacy `lives` field (v1 shape), discards it and sets
+ * needsMigrationModal = true so App.svelte can show the one-time modal.
+ */
+export function loadProgress() {
     try {
         const data = localStorage.getItem(STORAGE_KEY);
         if (data) {
             const parsed = JSON.parse(data);
+            // Detect v1 save shape (has `lives` field)
+            if (parsed.lives !== undefined) {
+                // Wipe legacy data, save clean v2 shape
+                const fresh = { ...DEFAULT_PROGRESS };
+                try {
+                    localStorage.setItem(STORAGE_KEY, JSON.stringify(fresh));
+                } catch (_) {
+                    // Storage full — proceed with in-memory defaults
+                }
+                return { progress: fresh, needsMigrationModal: true };
+            }
             return {
-                maxLevel: parsed.maxLevel || 1,
-                completedLevels: parsed.completedLevels || [],
-                levelStars: parsed.levelStars || {},
-                levelBestMoves: parsed.levelBestMoves || {},
+                progress: {
+                    maxLevel: parsed.maxLevel || 1,
+                    completedLevels: parsed.completedLevels || [],
+                    levelStars: parsed.levelStars || {},
+                    levelBestMoves: parsed.levelBestMoves || {},
+                },
+                needsMigrationModal: false,
             };
         }
-    } catch (e) {
+    } catch (_) {
         // Corrupted data, reset
     }
-    return { ...DEFAULT_PROGRESS };
+    return { progress: { ...DEFAULT_PROGRESS }, needsMigrationModal: false };
+}
+
+/** Legacy compat shim — returns progress only. Use loadProgress() for migration detection. */
+export function getProgress() {
+    return loadProgress().progress;
+}
+
+/** Whether the v2 migration modal has been acknowledged. */
+export function isMigrationAcknowledged() {
+    try {
+        return localStorage.getItem(MIGRATION_KEY) === 'done';
+    } catch (_) {
+        return true;
+    }
+}
+
+export function acknowledgeMigration() {
+    try {
+        localStorage.setItem(MIGRATION_KEY, 'done');
+    } catch (_) {
+        // ignore
+    }
 }
 
 // Calculate star rating: 3★ = ≤par, 2★ = par+1 to par+3, 1★ = completed
diff --git a/src/scenes/GameOver.svelte b/src/scenes/GameOver.svelte
index 2ba2e2a..b75ed91 100644
--- a/src/scenes/GameOver.svelte
+++ b/src/scenes/GameOver.svelte
@@ -1,21 +1,24 @@
 <script>
     import { getText } from '../lib/localization.js';
     import Button from '../components/Button.svelte';
-    let { navigate, level = 1, isLastLevel = false } = $props();
 
-    let title = $derived(isLastLevel ? getText('theEnd') : getText('gameOver'));
-    let desc = $derived(isLastLevel ? getText('ninjaFailed') : getText('caughtInLight'));
+    // flow: 'runComplete' (L11 cleared) | 'bittersweet' (L12 reached goal)
+    let { navigate, level = 1, flow = 'runComplete' } = $props();
+
+    let isRunComplete = $derived(flow === 'runComplete');
+
+    let title = $derived(isRunComplete ? getText('gameOver.runComplete') : getText('theEnd'));
+    let desc = $derived(isRunComplete ? getText('gameOver.runCompleteBody') : getText('ninjaFailed'));
 </script>
 
 <div class="gameover">
-    <h1 class:accent={isLastLevel} class:danger={!isLastLevel}>{title}</h1>
+    <h1 class:accent={isRunComplete} class:bittersweet={!isRunComplete}>{title}</h1>
     <p>{desc}</p>
     <div class="buttons">
-        <Button text={getText('tryAgain')} onclick={() => {
-            if (isLastLevel) navigate('MainMenu');
-            else navigate('Game', { level, lives: 3 });
-        }} />
         <Button text={getText('mainMenu')} onclick={() => navigate('MainMenu')} />
+        {#if isRunComplete}
+            <Button text={getText('levelSelect')} onclick={() => navigate('LevelSelect')} />
+        {/if}
     </div>
 </div>
 
@@ -29,7 +32,7 @@
     }
     h1 { font: bold 48px Arial, sans-serif; }
     h1.accent { color: var(--text-accent); }
-    h1.danger { color: var(--text-danger); }
+    h1.bittersweet { color: var(--text-danger); }
     p {
         font: var(--font-body);
         color: var(--text-secondary);
diff --git a/src/scenes/LevelSelect.svelte b/src/scenes/LevelSelect.svelte
index 0cb0999..1aac461 100644
--- a/src/scenes/LevelSelect.svelte
+++ b/src/scenes/LevelSelect.svelte
@@ -10,7 +10,7 @@
 
     function selectLevel(num) {
         if (num <= progress.maxLevel) {
-            navigate('LevelIntro', { level: num, lives: 3 });
+            navigate('LevelIntro', { level: num });
         }
     }
 </script>
diff --git a/src/scenes/StoryIntro.svelte b/src/scenes/StoryIntro.svelte
index b1e9f92..d56a7c6 100644
--- a/src/scenes/StoryIntro.svelte
+++ b/src/scenes/StoryIntro.svelte
@@ -9,13 +9,13 @@
         const el = document.querySelector('.story-scroll');
         if (el) {
             el.addEventListener('animationend', () => {
-                if (!scrollDone) { scrollDone = true; navigate('LevelIntro', { level: 1, lives: 3 }); }
+                if (!scrollDone) { scrollDone = true; navigate('LevelIntro', { level: 1 }); }
             });
         }
     });
 
     function skip() {
-        if (!scrollDone) { scrollDone = true; navigate('LevelIntro', { level: 1, lives: 3 }); }
+        if (!scrollDone) { scrollDone = true; navigate('LevelIntro', { level: 1 }); }
     }
 </script>