There are many collectibles in Kao the Kangaroo to find, and one of them are Heart Pieces. For those familiar with a certain green tunic wearing hero, yes, getting four Heart Pieces will grant Kao an additional full heart for his health. This page will detail the locations of all the Heart Pieces in The Dark Forest.
Heart Piece #1 Location
At some point during the level, you will pass through a large gate and then be introduced to the Frogster enemy. If you look just outside that gate, you should find a path leading upwards, to a hut that has a wooden door. Bust open that wooden door with any attack to find the Heart Piece inside.
Heart Piece #2 Location
As you continue through The Dark Forest, you will stumble upon a small cave not long after being introduced to the Fire Spitter enemies. This cave has a water puddle that you can safely navigate and will also have a little dead end. This dead end is being guarded by a spider that drops down from the ceiling. You can easily dispatch it by hitting the green orb-like object on the web, as hitting the spider itself does nothing (you can also just leave it alone). Go to the end of that dead end passage to find the Heart Piece.
Heart Piece #3 Location
You will be able to grab this final Heart Piece in The Dark Forest in the final room of the level. This is the room with all of the Frogsters in the bar-like area. It’s best to clear out all of the enemies first, so you don’t have to worry about getting knocked into the yucky water and forced to respawn. Once the coast is clear, look on the one side of the area to find a small island you have to jump to via a barrel to reach, which is where you will find the Heart Piece.