Super Mario Galaxy 2/World S/Mario Squared

The first Galaxy in World S is kind of throwback or even sequel to Super Mario Galaxy Toy Box galaxy. It's landscape feature Mario in it's 6 bit design as the ground for this galaxy for it's normal star, and 6 bit Luigi for it's prankster comet star.

Make Mario a Star
The objective in this level, is making all the ? marked tiles to ! ones.

While it sound simple, most of the level have disappearing tiles once stepping on them. There's no much a guide to how to do it but simply planning which way to go first. The advice is start from the north-east corner to the north-west corner, and then go back to the south ones. Just take the unlimited time to plan your steps well.

Once all the ? marked had changed, the Star will shown where you started the level. So make sure that the nearest disappearing tiles won't go off.

Luigi's Purple Coin Chaos
This level is considered one of the hardest level in the game. If you thought Make Mario a Star level was easy, this one is not. It's not only the fact that there's no shortage in the Purple Coins, you must collect them all. But also the game will give you 2 minutes to do it, and also a bunch of Shadow Mario will chase you.

This means that you must not only plan your steps carefully, but try at best not to miss any coin in any tile, not only as they disappear but also not to get hit by Shadow Mario. The advice is not to take all the closest purple coins nearby, but take the purple coins in the right and from there taking a long jump to the north-east corner, collect the purple coins there (there's also a coins that can be gathered by long jump only), and from there going north-west, south-west and then come back south-east to the beginning.

If you lost too much lives, take advice from Cosmic Roselina to show you the best plan (which is similar to how I have written). Good Luck.