KABOOM!!! Trophy in 4 Elements HD

As the trophy explains, you must create a chain of 30 of more pieces. This means that all 30+ pieces must be touching each other so you can link them all. Once you have 30+ pieces of the same color all lined up and next to each other, one after the other... start your chain and make a single non-stop line that goes through all of them up till piece #30 (at least) and then let go of the button so they all explode and both Boom! and KABOOM!! can unlock. This can be done on any level, but I found it easier to do on level 2. You might also want to try it on a higher level so you can use the Swap power up to set up pieces properly.