Initially, I was trying to sketch a bubble generate a program that each time the mouse clicked, a free moving bubble appear on the canvas. However, when I put the bubble drawing part into the mouseClicked() function, the newly created bubble does not move. So I change my program to the new game version: when the program runs, a free moving ball appears on the screen. Pressing the upper arrow to make the radius increase while the down arrow decreases the radius. Any other key was pressed while resetting the ball to starting radius. If the radius smaller than 0 or bigger than the canvas, the program will stop.
The video record of the sketch:
https://drive.google.com/file/d/1YvoSu5ToCa4h3q_UUq-2bWhPN3V7__lx/view?usp=sharing