Sudoku・ by Optime Software LLC is a long-standing, free-to-play mobile puzzle application designed to provide a high-quality, "frustration-free" Sudoku experience. Targeted at casual gamers who value classic gameplay without the friction of initial purchase costs, the app positions itself as a premium-quality alternative in a crowded market. The app’s core value proposition lies in its technical utility features, specifically its dual-keypad entry system and smart note-taking capabilities, which aim to streamline the solving process. However, despite its historical success and high aggregate rating, the product is currently facing a significant decline in user sentiment. Recent updates have introduced aggressive, unskippable advertising and controversial UI/UX changes that have alienated its long-term user base.