🎮 1. Difficulty Selection Screen

Available difficulty levels:

EASY

MEDIUM

HARD

EXPERT

After selecting a difficulty, the app loads a puzzle set from internal storage (JSON or DB) and starts the game.

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🔄 2. Continue Game (Resume)

Automatically saves all game progress:

Current board state (9×9 grid)

Notes (memo numbers)

Timer progress

Remaining lives

On app restart, a "Continue" button appears if saved data exists.

Uses SharedPreferences or Room Database.

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⏱️ 3. Timer & Pause System

Displays elapsed time (e.g., 00:12:51)

Pause button:

Freezes the timer

Blurs or dims the board

Shows a “Resume” button

Resume button unfreezes the timer

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🏆 4. High Scores

Stores the best clear time for each difficulty

After clearing the puzzle:

If faster than the previous record → show “New Record!” popup

Data stored using SharedPreferences or Room

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❤️ 5. Life System (3 Mistakes)

Player has 3 lives

When entering a wrong number:

Number turns red for a moment (error highlight)

Device vibrates briefly

One life icon disappears

When life reaches 0:

Bomb explosion animation

“Game Over” popup with Restart option

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🎉 6. Game Clear System

Upon completing the puzzle:

Show Thumbs Up icon animation

Display colorful confetti fireworks animation

Show Clear popup with:

“Restart”

“Go to Difficulty Selection”

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🔘 7. Button Features
✔ Undo

Uses a stack to store previous states

Multiple undo steps supported

✔ Eraser

Clears the selected cell

✔ Notes (Memo Mode)

Allows input of small candidate numbers

Toggle button: Note ON / OFF

✔ Hint

Fills in one correct cell

Optional limit based on difficulty

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🧩 8. UI / UX Enhancements
✔ Highlight System

Highlights:

Selected cell

Row & column

3×3 block

Same numbers on the board

✔ Error Feedback

Red numbers on wrong input

Short vibration feedback

✔ Modern UI Design

Soft pastel or dark theme

Rounded cards for grid and buttons

Material You / Material 3 styles

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📱 9. Modern App Icon

Possible styles include:

Minimal “9” or Sudoku block

Clean 3×3 grid design

Cute cartoon block characters

Premium blue / gold gradient icon