# Sudoku - ToolNPlay
> Free, distraction-free, tactile online Sudoku puzzle game designed for maximum legibility and speed. Deployed on sudoku.toolnplay.com.

## Overview
Sudoku by ToolNPlay delivers a clean, high-contrast, tactile 9x9 Sudoku experience designed for desktop and mobile web browsers. Built with vanilla JavaScript, procedural Web Audio API, and ToolNPlay's signature dark theme (Jetblack & Cerulean).

## Key Features
- **Crystal-Clear Board Legibility:** Flat, tactile 9x9 grid with prominent 3x3 block division and zero optical perspective distortion.
- **Dynamic Peer Highlighting:** Effortlessly scans matching rows, columns, 3x3 boxes, and all matching digits.
- **Pencil Notes Mode:** Take candidate notes in any cell with auto-cleanup when answers are confirmed.
- **Difficulty Tiers:** Easy, Medium, Hard, and Expert with guaranteed unique mathematical solutions.
- **Persistent 24-Hour Hint Economy:** 2 free hints per 24 hours (tracked via cookies & local storage). After 2 free hints, every single hint strictly requires viewing an ad. If no ad is available or not completed, no hint is granted.
- **Real-Time Error Checking:** Strict 3-mistakes mode or relaxed unlimited play.
- **Web Audio API:** Crisp sound effects generated procedurally with zero audio asset latency.
- **Dark & Light Theme:** Matches ToolNPlay.com with instant theme synchronization.

## Monetization & Analytics
- **Google AdSense:** Client ID `ca-pub-9704521076577901`, Slot `3518047878` (Games-TNP)
- **Google Analytics (GA4):** Measurement ID `G-6K6TSD5RBN`

## Core URLs
- [Play Sudoku](https://sudoku.toolnplay.com/): Main game interface.
- [How to Play Guide](https://sudoku.toolnplay.com/how-to-play.html): Rules, techniques, and shortcuts.
- [About ToolNPlay](https://sudoku.toolnplay.com/about.html): Tech stack, mission, and architecture.
- [More Games](https://games.toolnplay.com): Discover more games on ToolNPlay.
- [Contact Support](https://toolnplay.com/contact): Official ToolNPlay support.
- [Privacy Policy](https://sudoku.toolnplay.com/privacy.html): GDPR, CCPA, Google AdSense & analytics disclosure.
- [Terms of Service](https://sudoku.toolnplay.com/terms.html): Usage terms and guidelines.