The position of Venus depends on
• the radius of its orbit, rV = 120, fixed
• and its angle, aV = -PI/2, the starting value
To make Venus move around its orbit just change aV
The code aV = aV + PI/40;
is an instruction to increase aV by PI/40 radians (about 4.5°)
Remember that the frameRate is 60 frames per second.
Venus will advance by about 4.5° every 1/60 second.
which is about 270° per second.