Find this doll right after beating the third castle.
2-M
After completing the castle, jump up to the platform to the left, and use the Faster Boots to leap over the gap to the column ahead. Jump on the pipe before the wall to make a moon appear. Just beyond the pipe, you can jump on the floor to make the last two block disappear, and locate a Hao Doll.
2-L
The small pipe below the platform contains a star which you must double back to collect.
2-K
If you work your way back along the bottom path and shoot the wall to the right, you will locate a Double Score icon.
2-J
Don't get distracted by the moon up above, as that is only obtainable from the first world. The small pipe before the shallow pool of water contains a star. Use the two clouds to maneuver over the water and reach the platform beyond.
2-I
Avoid the skulls on the floor and collect the sign post. The first pipe contains a star. Pushing down on the second pipe will transport you all the way back before the water in 2-J. Be sure to push left as you fall to the ground beyond the bottomless pools of water so that you don't drown.
2-H
The first pipe beyond the water contains a star, as does the third pipe.
2-G
Clear out the Snakes and Scorpions before you attempt to pass through the tunnel. When you reach the trampoline block, time your trip to the ledge on your right carefully; you'll want to begin moving right as you begin to fall back down to the trampoline so that you clear the block above your head, or you will fall in the water.
2-F
The middle pipe contains a star. Use the cloud to travel over the water and up to the small block in mid-air. The top block before the (If you happen to fall down on top of the big pipe, the wall to the right can be shot out, but you'll have to travel back through the water.)
2-E
Be aware of the Hedgehogs which will drop down from the building in the town. The first pipe before the skull contains a star.
Collect the lamp and charge to the castle.
2-D
Collect the sign post at the start of this section. Watch out for the Hedgehog that will drop down the steps. The pipe between the skulls will take you all the way back to 2-E if you push down. Jump up to the small blocks above the water. Wall bounce off the first wall of bounce blocks to get between the two walls. Then triangle jump off the right wall, and wall bounce over the left wall to proceed.
2-C
The first pipe contains a star. Shoot out the second set of blocks on the floor to reveal a Magic Lamp. Collect it and begin racing to the left.
2-B
The first pipe after the lamp contains a star. Shoot out the bottom blocks of the large left arrow structures.
2-A
The second pipe before the castle contains a star. Collect the sign post and enter the castle.
Completing this castle depends on collecting the pink potion that you can see in the upper level upon entering the castle. From the start, head left, and jump up to the middle level on the right and pass through the door.
Destroy the blocks this way to collect the key.
Back layer to Magic Medicine
The next trick is to make it up to the upper level from the middle level. This can be done as long as you do not shoot the bottom block of the wall to the left of the door you arrived in. If you jump in front of the wall, you can break a hole in the ceiling, as well as one block to the left. By leaving the first block alone, you can jump up into the newly created gap. However, one block to the left of that floor block, you will locate a key that you need to collect. Grab the key and use the first block to jump up to the level above. Then head right. Before you pass through the exit, you can expose a Double Score icon from behind the pillar below the door. (Note that if you travel along the bottom level of this layer, you can shoot out the right wall and expose a path to the back layer from door 4. If you like, you can collect a key and exit out from this area and back track to the third door. It's not much faster, and you will miss the opportunity to collect a Hao Doll.)
Front layer to door 1
Collect the Magic Medicine which gives you the ability to knock ice blocks away with your magic. Then jump on the floor to the right of the door to expose a hole to the level below. Take the lower level and run to the right. You will find the first door beyond an ice block over a trampoline block. Taking it is voluntary. (If you want to avoid dealing with the mini-boss, you can collect a key from the previous door that led to the Medicine.)
Back layer of door 1
Head left and you will encounter the mini-boss of this castle, a snail. The snail is a difficult foe since it can fire projectiles in many directions and it likes to change levels. If you stay above or below it, not only will you be safe from the projectile it fires, but it will eventually return to your layer where you can briefly shoot it before it moves away again. Defeat it and collect the key. Then head left and find the opening to the lower level. Walk back to the right where you see a wall over a bed of spikes. Shoot out the wall until you reveal a moon. You'll have to brave the spikes in order to collect the moon, but it's usually worth it. You can't proceed to any exit door, so you'll have to return the way you came.
Shoot out the blocks above to reveal this doll.
Front layer to door 2
Assuming you obtained the Magic Medicine, you can knock the ice block off the trampoline block and use it to bounce up to the high level to the right. Drop down to the lowest level after the pool of water and shoot at the ceiling at the dead-end to reveal the location of a Hao Doll. Then climb up to the top layer, and drop down the steps that follow. Shoot the flowers if you like, then climb back up the other set of steps. Shoot away and Scorpions on the path ahead of you, and then you must leap over the two gaps and remain on the highest level to proceed. Once again, entering the second door is entirely voluntary.
Back layer of door 2
Head right and shoot the flowers if you like. You'll be taken to the middle level. On your way back, you will see a single flower in a mantle. Jump above it and break a hole in the floor and use the mantle to climb up. There is a moon behind the pillar, which you can kick left and chase. It will stop at a barrier, and you can collect it, but do not jump down below of you will be forced to return through the first door. Instead, return left, and head through the left exit door. In the front layer, you will have to walk left past some flowers, and then jump up to the middle level and shoot out the walls to the right until you reveal a 10,000 point broom at the very end. You can jump up at the ceiling above the broom to create a hole that will allow you to proceed to door 3.
Front layer to door 3
Whether you leap over the gap, or move the ice block and use the trampoline block, or create a hole in the ceiling over the broom, proceed to the right. Take the high path that ends up in a dead end, and jump one block to the left of the suspended block in the middle level to break a hole in the floor. Drop down to the suspended block, and continue moving to the right to keep your momentum in order to reach the steps beyond the gap. Drop down to the lowest level, proceed to the steps on the right, and jump up to the middle level. Push an ice block from behind the pillar to the left so that it stops at the edge of the platform. Use this block to leap up to the high level to the right. You will see the third door in the gap below. While you will have to visit the back layer of this door, you don't necessarily have to take the door below. You can jump on the floor of the high level beyond the gap to drop down to the section that contains the Heart.
Back layer of door 3
Move to the left to fight the mini-boss snail and collect a key. Be careful if the key drops behind a pillar as collecting it is likely to kick it away instead. Continue right to access the top level, then return to the left and leap over the spike floors. Drop down to the lower level, and shoot out the left wall which leads to a moon beyond a pool of water. Carefully leap over the water to collect the moon, then pass through the nearby door. In the front layer, shoot up at the floor beneath the Heart and collect it as it falls down. Then you must return through the door, fight a snail again and return through the right exit to continue.
To the exit
The fourth door is entirely optional, as the exit from the castle is all the way to the right in the front layer. You need only travel along the top level until you reach the fourth door, and leap over the gap, or use the trampoline, to travel beyond and continue to the right until the exit comes into sight. The only thing you'll find in the back layer of the fourth door are a mini-boss and some flowers.
