Super Mario Galaxy/Matter Splatter Galaxy

Matter Splatter Galaxy is accessible from the Garden observation dome. You need 50 Stars to enter, one of which must be from completing Heavy-Metal Mecha Bowser in Toy Time Galaxy.

Star 1: Watch Your Step
Avoid falling into space by jumping on the ground when it has not disappeared. (For this part, the ground disappears every 3 seconds). Avoid the witches or defeat them, (it's easier to just avoid them). Once you pass that go through the green pipe. You will then be presented with the same concept except with the witches and instead you must wall jump your way up with precision timing. Then you must go across disappearing land and work your way up to the top and go through the green pipe, (wall jump again, travel right, wall jump again, go left where 1 witch will be presented and keep going left to reach the pipe). Get the spring ability and then high jump by pressing "A" at the right time to get the Yellow ? coin. You will then have to bounce your way up (be patient and wait until you can see the next edge). You should see yet another Yellow ? coin which will make a lot of star bits appear. As the ground moves up you can see two planks, jump onto either one of them. Jump onto the rocking swing where you will launch yourself with a launching star, and then will go through a green pipe. Travel through the disappearing land and you will find two witches of which you can either ignore or you can defeat. Continue going until you reach the star and you have completed that galaxy.

Did you find? A coin on the far left of the second layer in the green pipe zone? A 1-up life while you were a spring in the rocking swing?