Gather 2+ blocks of the same color and click on them to have an explosion that let the other fall according to the gravity.
You have access to three bonus blocks : gravity bonus changes the gravity direction, paint bonus changes the color of some blocks and finally the spawn bonus gives you some new blocks.
When you explode 2 blocks, you have 0 new one, 3 => 1, 4 => 2 etc, always x-2 new blocks. so try to make the biggest set !

Enjoy !