Gameplay itself is simple. The goal of the game is to clear the board of bubbles using a certain number of taps. Each time a bubble bursts, it releases bubbles in four directions. When these bubbles hit other bubbles, they either pop those bubbles (which in turn release four more bubbles), or they turn those bubbles into the next colour.
The bubbles come in four colours - red bubbles, which pop with one hit; green bubbles, which pop with two hits; yellow bubbles, which pop with three hits, and blue bubbles, which pop after four hits. When a green bubble is hit, it turns into a red bubble; when a yellow bubble is hit, it turns into a green bubble; and so forth.
The first few levels - full of red and green bubbles - are pretty simple and let you get a feel for the game. But it gets much harder much faster. Many levels take a lot of strategizing, as you're given only two or three taps with which to clear the board. The game has a whopping 6000 levels - 60 packs of 100 levels each - to get through, and they're all free.
There's also an arcade mode. In this mode you're presented with a random board and given a certain number of taps to clear it. However, with each bubble that pops, you're given an extra tap.