Complete the Seeing Stars DLC main campaign.

Complete Levels 1-32.

Complete the bonus finale in the Seeing Stars DLC.

Find all 100 solutions in the Seeing Stars DLC (100% Completion).

Make sure you get every star in every level. If you're struggling, feel free to use my walkthrough guide:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=3275215426

Thank you to adam55502 for letting me know that "For Level 32, all three solutions/stars have to be done in one go. Personally, I did not do this originally and thus did not get the 100% achievement even will all the stars."

Introducing our newest flavour.

On Level 22 there is a lollypop and four pieces of gum. Attach the gum to the lollypop.

I like my drinks lukewarm.

On Level 10, just take all of the ice, out of the glasses:
(Thanks Kaidarra!)

I'll go left, you go right.

On Level 24, group the pieces by the direction they are looking:
To make it clearer, here is where all of the pieces should go:
Middle: red wizard, yellow wizard, blue wizard, blue pennant. (4 pieces)
Right: orange cowboy, blue archer, blue goblin, yellow swordsman, black swordsman, blue camel. (6 pieces)
Left: (all the rest) i.e.: black archer, yellow pennant, green goblin, red goblin, green swordsman, blue cowboy, black bear, black cowboy, red giraffe, orange pennant, orange rhinoceros, blue archer. (12 pieces)

(Thank you Racknore!)(Thank you oldladygreybun for the screenshot and list!)

Thank you 荒ぶる for letting us know that you don't have to put the pieces in the boxes, they just need to be in separate piles:

Solve the Music Box with the Counter set to the hidden number.

On Level 28, set the number on the counter to 8, then solve the puzzle as normal.

(Thank you Majora!)

That doesn't look like anything.

On Level 32, place the gems so that the corners of the clear gems with no cutouts are in the middle:
(Thank you alex!)

All for one.

On Level 11, put all of the toppings onto one of the pizza slices.

Ouch, that's sharp.

On Level 27, there's a box cutter. Just activate the box cutter to bring out the blade and then click on the blade.

Thank you for checking out my guide! ♡