Press and hold to grow a bubble, then let go to drop it. It falls and settles on whatever is already down there. Cover 60% of the field with the bubbles you are given and you win the round.
A bubble stops growing the moment it touches a wall or the pile, and bursts if a hazard reaches it — a red ring warns you as one closes in, and time slows just before impact, so you can still let go in time.
Three chapters, each adding one rule. Chapter 1 is the open field. In chapter 2 every colour keeps an area only its own bubbles may start in, with open water between them for everyone. In chapter 3 those areas drift and close in while you play.
270 levels and 234 challenges. Every bubble you finish a round without spending becomes a star, and stars open the challenges and the chapter that follows.
A classic physical game. Grow bubbles, fill the field, dodge the hazards.