iOS - Bug Can't use Plunger during Defeat the Genie mode.

Tried out the game on iPhone, its a bit hard to aim the left and right loops but eventually I got to the Defeat the Genie mode.
The aim of this mode is you get unlimited balls, and keep hitting the yellow indicators. with one ball on the playing field, I could not find the option to put more balls in.
anyone else having this problem?

I had multiple balls on the playfield, but I can't remember how they got there. Auto launch, I think?

It auto launches the balls. Which is ok in general, although you might prefer to launch them in your own tempo to better time the Genie-shots or if you want to play with 3 balls on the table and 1 in the plunger (as the balls tend to get into eachothers way). A launch button, similar to the future MM one, would be preferable but not a necessity of life.

If you keep balls in the plunger, time is running faster against you so in general it's better to have them all in play to win the battle.