Only the letters A to Z. Each bubble carries a single letter, and either upper or lower case will pop it; digits, punctuation and shortcut keys are ignored, and pressing a letter that is not on screen costs you nothing.

You start with five lives and earn 10 points for every bubble you pop. A bubble that floats past the top of the screen costs one life, and at zero lives the game ends and shows your final score. Nothing carries over: Try Again restarts at zero points with five lives.

Yes. A row of on-screen A to Z keys sits along the bottom, and tapping one works the same as pressing the physical key. The on-screen keys are hidden on very short screens (under about 500 pixels high), where you would type on a real keyboard instead.

No, there is one endless mode with no level or difficulty picker. It speeds itself up instead: as your score rises, bubbles float upward faster and spawn more often.