CosmDr Wi is a vertical letter reaction challenge mobile game that cleverly combines time-limited levels with precise tapping gameplay. A target letter will randomly appear in the centre of the screen, and players must quickly select the correct answer from the 26-letter keyboard below within the time limit. Each correct answer scores points, and the countdown gradually shortens, increasing the difficulty. Wrong taps or running out of time count as mistakes, and the game ends after three mistakes. The game also includes pause and resume, restart, high score records and vibration feedback. The rules are simple and the pace is fast, making it perfect for casual play during short breaks or for challenge-seeking players aiming to push their hand-eye coordination to the limit.