Bubble Crush has 4 mode which list down below.
Classic
Crush the bubbles of the same color by tapping one of them if they are in a block of 3 or more. A block can be formed in minimum of 3 for levels 1 to 5, 4 for levels 6 to 10 and 5 there after.
Connectors are introduced randomly from top which will help you to connect either vertical or horizontal bubble blocks of different colors.
Coins are introduced on board for each 100 bubbles are crushed. You will need to set out the coins at the slots to clear the level.
Clear All
You will need to clear the board by crushing all bubbles. No new bubbles are added from top, but you may run into deadlock if not played wisely!
Bombs are introduced to help you clear the level which would crush all the bubbles surrounding it. It will blast off the 4 bubbles vertically and 4 bubbles horizontally!
Filled
Complexity will increase as the new bubbles will get filled from bottom and you would need to make hurry to finish the level. If the level of bubbles reaches the top, you are gone.
Bombs will help you often to clear out the level. It would blast off the bubbles same as in "Clear All" level.
No time limits to complete the level but instead some number of bubbles are crushed and you are done to next level!
Timed
This is almost same as "Filled" mode but there are time limits to complete the levels.
You need to complete each level in maximum of 2 minutes and that should be enough!