The free iPhone app for today, as reported by FreeAppADay, is Mastermind. This mobile version of the 1970 board game created by Mordecai Meirowitz brings all the code breaking fun of the original to your fingertips on the iPhone. Play as a code-breaker, and guess the secret code in as few turns as possible using pattern setup in both color and order. The new version features an extra mode to facilitate use by the color blind; in addition to Color mode, you can now select Symbol mode. Mastermind offers four levels of difficulty, updated translations in four languages (English, German, French and Polish), and a clean and shiny new interface.
This app is usually $1.99 on the app store. It will be free only until the end of today, so make sure to grab it while you can.