There are a number of collectibles to find in Kao the Kangaroo, with one of them being Crystals. Each level in the game will have these blue Crystals hidden throughout them, all of which will contribute to 100%. This page will give details on the locations of the Crystals in Hopalloo Island.
Crystal #1 Location
Right by the entrance to Walt’s Dojo, which is where you end up upon finishing that level the first time, there are two buildings that will have their doors open. Inside one of those buildings will be both a Scroll, and this Crystal, which will be in the corner.
Crystal #2 Location
After collecting the previous Crystal, go back out onto the deck, then find the stairs leading down on the far end, by Walt. As soon as you reach the bottom of the stairs, go underneath the deck and to the far end, which should be underneath the entrance to the Dojo level. You will find this Crystal by the waterfall there.
Crystal #3 Location
Return to Walt back at the beginning and head down the stairs behind him, then follow the trail towards the long bridge with the paint on it. Look to the one side to see the artist’s house and underneath it are two swings. On one of those swings will be the Crystal.
Crystal #4 Location
Double back to the painted bridge and cross it this time, opting to go up the hill on the other side. At the top of the hill will be a house, which has a Scroll inside it. In that same house will be the Crystal in the corner.
Crystal #5 Location
Drop down to the beach below you, from the previous spot, and locate the smaller hut at the end of the pier. This will be the fisherman’s place and you need to get onto the roof of it. Find any item you can stand on, then double jump and use the tail spin to get the tiny bit of extra height needed to get onto the roof. There will be a sign up here and the Crystal will be on that sign.
Crystal #6 Location
While still standing on the roof of the fisherman’s hut, look towards the bigger house on the beach (this is your house) and locate the lone barrel out in the water. Make your way towards that lone barrel to find the Crystal on top of it.
Crystal #7 Location
Go to the entrance to your house and look across from it to spy a house with a farmer outside working. Head to this house and go inside to find the Crystal floating above the hammock.
Crystal #8 Location
Not too far from the previous location (the farmer’s house) is the shop, which sits on top of a large deck. Underneath that deck will be the Crystal floating in mid-air. It will be on the side that is facing the small pond in the middle of the island, with the rocks surrounding it.
Crystal #9 Location
Go to the shop now and pretend like you were going to purchase something. If you check the corner of the shop area, next to the costume closet, you will find the Crystal.
Crystal #10 Location
Not too far from the shop, there is an outdoor set of tables and next to them will be a small makeshift gate. Sitting on top of the gate will be the Crystal. You can simply jump up and grab it from the ground.
Crystal #11 Location
Near the previous Crystal, there is a large house and the Crystal will be on top of that house. To get to it, look for the stump next to the house, then use that to reach the ledge next to it. From there, you should be able to jump on top of the house and grab the Crystal.