This is a graphical output challenge where the task is to give the shortest code per language. I will maintain a list of the best answer for each language at the bottom of this question.

Task

Your code should plot a single purple pixel, moving clockwise round a circle. It should take exactly 60 seconds to make a full journey round the circle and should continue indefinitely. Nothing else should be shown on the screen except for the pixel. The width of the circle should be 0.75 (rounding suitably) the width of the screen or window and the background should be white.

Your code should be a full program.

Languages and libraries

You can use any language or library you like. However, I would like to be able to test your code if possible so if you can provide clear instructions for how to run it in Ubuntu that would be very much appreciated.