Perceptron allows you to out-guess a random number generator.
The user clicks on one of 4 squares (buttons), and the program informs the user which square they should have clicked on. The user has 28 guesses, and his/her performance is reported progressively.
The correct guess is shown by hiding the wrong buttons, and highlighting the correct buttons for 666 milliseconds.
If the user so desires, above average performance can be attributed to ESP.
This program can serve as a simple example of Qt buttons, timers, and of code that will build on both Linux and Windows.