Now I look at your last sketch
here is your mistake:
The upper screen border is not height but 0 (zero)
The lower part is height.
(The point 0,0 is upper left corner)
Hence you want
//Tried to reset riseStart when the small ball exits the window to spawn a new ball.
if (riseStart < 0) {
or
//Tried to reset riseStart when the small ball exits the window to spawn a new ball.
if (riseStart < bsize2) {