This page offers a guide on Purple Coins on the Puzzle Cube in Gusty Garden. To have access to this level, a Purple Comet must be in orbit of the galaxy, and this will only occur once the main storyline has been completed.
Collect 100 Purple Coins
This is certainly one of the easier Purple Coin levels as there are 150 possible Purple Coins to pick up but you still only need to collect 100. This means you don’t have to worry about picking up every single coin on each face of the Puzzle Cube. You will need to pick up at least 100 Purple Coins in two and a half minutes. There are so many easily accessible coins on the cube that you don’t need to go for awkward jumps to grab one or two hard-to-reach coins. Instead, you want to focus on running around the cube collecting as many of the easy coins as you can in the allotted time. Also, watch out for the Goombas!
Remember, within the two and a half minutes, you’ll also need to run back to the starting side of the cube to pick up the Power Star above the fountain. It’d be handy if you remembered which direction you went so you can quickly get back without getting lost.