Level 2: Extra health
Use the following steps to find a hidden heart items that will give your ninja two extra counters on his/her life bar. The heart is on a tree high above where you start. To obtain it, climb the cliff to the far right when you have the Mantle (cape) and Ninja Sandals tools. At the top of a super-jump, glide until you reach the far left edge of the screen, then drop down to get it.
Level 4: Extra health
Use the following steps to find a hidden heart items that will give your ninja two extra counters on his/her life bar. Start the level and proceed to kill the first seagull. After disposing of the second two gulls, assuming you have the Ninja Sandals and the Tabi (the socks), super-jump to the first platform on that mast. Then use a regular jump and stick to the bottom of the second platform. You should automatically pick up the second heart although it is on top.
