diff --git a/dev-dist/sw.js b/dev-dist/sw.js
index 8d96cbc..24f2c2f 100644
--- a/dev-dist/sw.js
+++ b/dev-dist/sw.js
@@ -82,7 +82,7 @@ define(['./workbox-7a5e81cd'], (function (workbox) { 'use strict';
    */
   workbox.precacheAndRoute([{
     "url": "index.html",
-    "revision": "0.kkc80cp3p5o"
+    "revision": "0.n1n8rjsg38"
   }], {});
   workbox.cleanupOutdatedCaches();
   workbox.registerRoute(new workbox.NavigationRoute(workbox.createHandlerBoundToURL("index.html"), {
diff --git a/src/components/GameBoard.vue b/src/components/GameBoard.vue
index 142528f..0c43e0b 100644
--- a/src/components/GameBoard.vue
+++ b/src/components/GameBoard.vue
@@ -247,10 +247,10 @@ watch(() => store.size, async () => {
       <div class="corner-spacer"></div>
       
       <!-- Column Hints -->
-      <Hints :hints="colHints" orientation="col" :size="gridCols" :activeIndex="activeCol" />
+      <Hints :hints="colHints" orientation="col" :size="gridCols" :activeIndex="activeCol" :completedLines="store.completedCols" />
       
       <!-- Row Hints -->
-      <Hints ref="rowHintsRef" :hints="rowHints" orientation="row" :size="gridRows" :activeIndex="activeRow" />
+      <Hints ref="rowHintsRef" :hints="rowHints" orientation="row" :size="gridRows" :activeIndex="activeRow" :completedLines="store.completedRows" />
       
       <!-- Grid -->
       <div 
diff --git a/src/components/Hints.vue b/src/components/Hints.vue
index 398689d..70c7eb8 100644
--- a/src/components/Hints.vue
+++ b/src/components/Hints.vue
@@ -16,6 +16,10 @@ defineProps({
   activeIndex: {
     type: Number,
     default: null
+  },
+  completedLines: {
+    type: Array,
+    default: () => []
   }
 });
 </script>
@@ -34,6 +38,7 @@ defineProps({
       class="hint-group"
       :class="{
         'is-active': index === activeIndex,
+        'is-completed': completedLines[index],
         'guide-right': orientation === 'col' && (index + 1) % 5 === 0 && index !== size - 1,
         'guide-bottom': orientation === 'row' && (index + 1) % 5 === 0 && index !== size - 1
       }"
@@ -81,6 +86,15 @@ defineProps({
   height: 100%;
 }
 
+.hint-group.is-completed {
+  opacity: 0.5;
+  background-color: var(--hint-bg);
+}
+
+.hint-group.is-completed .hint-num {
+  color: var(--text-muted);
+}
+
 .col .hint-group {
   flex-direction: column;
   padding: 4px 2px;
diff --git a/src/stores/puzzle.js b/src/stores/puzzle.js
index 0d701f6..f518186 100644
--- a/src/stores/puzzle.js
+++ b/src/stores/puzzle.js
@@ -56,6 +56,31 @@ export const usePuzzleStore = defineStore('puzzle', () => {
     return Math.min(100, (filledCorrectly.value / totalCellsToFill.value) * 100);
   });
 
+  const completedRows = computed(() => {
+    if (!solution.value.length || !playerGrid.value.length) return [];
+    const rows = solution.value.length;
+    return Array(rows).fill().map((_, r) => {
+      const targetHints = calculateLineHints(solution.value[r]);
+      const playerLine = playerGrid.value[r];
+      return validateLine(playerLine, targetHints);
+    });
+  });
+
+  const completedCols = computed(() => {
+    if (!solution.value.length || !playerGrid.value.length) return [];
+    const rows = solution.value.length;
+    const cols = solution.value[0].length;
+    return Array(cols).fill().map((_, c) => {
+        const col = [];
+        for (let r = 0; r < rows; r++) {
+            col.push(solution.value[r][c]);
+        }
+        const targetHints = calculateLineHints(col);
+        const playerLine = playerGrid.value.map(row => row[c]);
+        return validateLine(playerLine, targetHints);
+    });
+  });
+
   // Actions
   function initGame(levelId = 'easy') {
     stopTimer();
@@ -408,7 +433,9 @@ export const usePuzzleStore = defineStore('puzzle', () => {
     currentDensity,
     markGuideUsed,
     startInteraction,
-    endInteraction
+    endInteraction,
+    completedRows,
+    completedCols
   };
 
 });
diff --git a/src/stores/puzzle_completion.test.js b/src/stores/puzzle_completion.test.js
new file mode 100644
index 0000000..8d7c0b8
--- /dev/null
+++ b/src/stores/puzzle_completion.test.js
@@ -0,0 +1,70 @@
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { setActivePinia, createPinia } from 'pinia';
+import { usePuzzleStore } from './puzzle';
+
+describe('Puzzle Store - Completion Logic', () => {
+  beforeEach(() => {
+    setActivePinia(createPinia());
+  });
+
+  it('should correctly identify completed rows and columns', () => {
+    const store = usePuzzleStore();
+    
+    // Setup a simple 2x2 puzzle
+    // Solution:
+    // 1 0
+    // 0 1
+    // Row Hints: [1], [1]
+    // Col Hints: [1], [1]
+    store.solution = [
+      [1, 0],
+      [0, 1]
+    ];
+    store.playerGrid = [
+      [0, 0],
+      [0, 0]
+    ];
+    
+    // Initially nothing is completed
+    expect(store.completedRows).toEqual([false, false]);
+    expect(store.completedCols).toEqual([false, false]);
+    
+    // Fill first row correctly: 1 0
+    store.playerGrid[0][0] = 1;
+    store.playerGrid[0][1] = 0;
+    
+    expect(store.completedRows).toEqual([true, false]);
+    
+    // Fill second row incorrectly (too many filled): 1 1
+    store.playerGrid[1][0] = 1;
+    store.playerGrid[1][1] = 1;
+    
+    // Row 2 hint is [1], user has [2]. Should be false.
+    expect(store.completedRows).toEqual([true, false]);
+    
+    // Fix second row: 0 1
+    store.playerGrid[1][0] = 0;
+    store.playerGrid[1][1] = 1;
+    
+    expect(store.completedRows).toEqual([true, true]);
+    
+    // Check columns
+    // Col 1: 1, 0 -> Hint [1]. Matches.
+    // Col 2: 0, 1 -> Hint [1]. Matches.
+    expect(store.completedCols).toEqual([true, true]);
+  });
+
+  it('should mark row as completed if constraints are met even if wrong position', () => {
+    const store = usePuzzleStore();
+    // Solution: 1 0 0 (Hint 1)
+    store.solution = [[1, 0, 0]];
+    store.playerGrid = [[0, 0, 0]];
+    
+    // User puts 0 0 1 (Hint 1)
+    store.playerGrid[0] = [0, 0, 1];
+    
+    // Should be marked as completed because it satisfies the hint "1"
+    expect(store.completedRows).toEqual([true]);
+  });
+});
diff --git a/src/utils/large_grid_solver.test.js b/src/utils/large_grid_solver.test.js
index 43a6299..10907a7 100644
--- a/src/utils/large_grid_solver.test.js
+++ b/src/utils/large_grid_solver.test.js
@@ -39,6 +39,6 @@ describe('Large Grid Solver', () => {
         console.log('Result:', result);
         
         expect(result.percentSolved).toBeGreaterThan(0);
-        expect(result.difficulty).toBeDefined();
+        expect(result.difficultyScore).toBeDefined();
     });
 });