look below!

(c) xdarkzerox
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HEART PIECE GUIDE
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1.	Blast Hornet
	Requirements: NONE
	When you fight the big ship outside, there should be a sub boss door.
	Instead of going in, go up to the top and get the HP.

2.	Volt Catfish
	Requirements: Leg Upgrade 1
	When you go up and the elevator like thing for the first time, keep 
	going up and go right. Air dash to it and back.

3.	Tunnel Rhino
	Requirements: Arm Upgrade 1, Triad Thunder
	When you go up to the part where it is a bare screen besides the rock
	thing and an open path to the right, go right. Charge up the TT and
	drop the boulder to get the HP.

4.	Acid Seahorse
	Requirements: NONE
	When your in the sewers and are going up, keep going up to the very top
	and get the HP up there.

5.	Crush Crawfish
	Requirements: Chimera Armor
	At the very beginning of the level get the armor and go down the plunge. 
	Go to the far right at the plunge and there will be a weak wall. There is
	a HP in there.

6. 	Gravity Beetle
	Requirements: Beat Blast Hornet
	The place changes after you beat Blast Hornet. At the very beginning (in the
	building) go to the top left and get the HP.

7.	Blizzard Buffalo
	Requirements: Chimera Armor
	When you get the armor thingy at the first time, go and see the ice blocks right
	next to the place where you get the armor. Destroy them and get the heart piece.

8.	Neon Tiger
	Requirements: NONE
	At the end of the level instead of going through to the boss go up to the HP.