100% Route
Note: this page was adapted from swordsmankirby's guide. Some strats may be outdated.
2-1
A mostly straightforward level with one annoying powerup combination.
After Whispy Woods, you should have double fire, and if not, there is a fire enemy towards the beginning that you can grab. The three clips show the double fire route for the first room. The route is designed so that you don't land on any enemies during the recovery period between double fires.
Once inside, float up to the ceiling and double fire across while grabbing Shard 1. A safer strat that's easier for getting the right height is shown on the right. In both instances, use the star piece as a visual cue. Afterwards, grab stone on the Cairn enemy below after throwing away double fire.
The Kacti miniboss takes four hits and is straightforward with the rock powerup. The fastest way to grab Shard 2 is to use the powerup twice, ending farther left by the time of the fourth hit. Note that the animation where Kirby comes out of stone form also does damage and even has a larger hitbox. An easier strat, as shown on the right, just involves standing underneath the miniboss in stone form.
After exiting the autoscroller, there will be a cliff and a hill. Puffing right before hitting the ground cancels the nosedive animation, and since both uphill and downhill slopes slow down Kirby, jumping prevents you from losing speed. By far the scariest part of this level is combining with the Sparky at the end of the hill. There are many ways the Sparky can move, and missing the throw means resetting the level. Afterwards, run back across the hill and break the barrier with the yoyo to get Shard 3.
After climbing the hill once more, make it through the gauntlet of enemies. It's fastest to go underneath, as shown on the left, but floating up and running on the blocks doesn't lose too much time, either. The yoyo is helpful for clearing out enemies, but keep in mind that you get sent back to walking speed after using it.
2-2
Wait for the first column to fall and run underneath the rest. You can get underneath the first column, but it requires triggering it late with a precise jump. Waiting gives you time to throw away the yoyo powerup, which is useful for clearing the Sparky and Kacti enemies earlier in the level. If you're not comfortable with jumping underneath the Bouncys (middle), you can keep the powerup longer and get rid of it later (right).
Navigate through the mini maze to get Shard 1. There are several possible variations not shown here, such as floating up versus jumping up, or changing where you use fire.
In the next room, fire across the abyss to get Shard 2. In the next room, I like to do one fire on the ground to get the right spacing for avoiding the Kapars, but this requires relatively consistent single fire canceling. Take the last of the crushing platforms up to get closer to the exit.
In the Dedede section, it's faster to jump up the chains instead of climbing up them. It's easiest to damage boost off of the Galbo's fire breath to get up, but if you're low on health it's possible to jump past it. After grabbing Shard 3, jump before the pit to both save time and to avoid waking up the other Galbo too early. In some of the chain jumping sections, you can reduce your horizontal momentum by turning around twice to grab the chain at a better location.
2-3
Before entering the level, backtrack to 2-2 to get drill.
In the first room, use drill to get running speed as you enter the level, but keep in mind that you can get stuck on the entrance. Drill is useful for clearing out the many enemies in the beginning of the room. The first instance is using the drill on the first set of Boneheads. Depending on when you started the drill at the very beginning, it's possible to clear all four of them before letting go of the drill, but since it travels faster than you once you let go, you might as well do it as early as possible. The second drill comes after the Galbo, right before the block. If you do it too early, the second Bonehead might not get hit.
Also in this section is a rare exception to the slope mechanic. Since they appear to be flowing hills of sand, it's faster to run down these small slopes instead of jumping over them. Once you reach the big skeleton, use the drill to break the stone block, get rid of your powerup, and grab Shard 1. After dropping into the hole, take the path to the left. In the miniboss strat shown here, the third fire attack skims the bottom of the Fishbone so that the fourth fire (which is shorter and also slowed down by holding right) lands you right on the exit. Four "direct" hits is probably less than a second slower. After the fight, grab Shard 2 on the left.
The next two rooms are just tests of single fire, but there are some small optimizations at the exits. In the first of these two rooms, it's possible to slide from flat ground onto the slope, causing you to get into the loading zone faster than just sinking in the water. For the other room, try to spend as little time in the water, but don't go too far to the right or else you'll waste time sinking in the water.
The water sections can be sped up a little bit with a few fires. For Shard 3 you can duck in the crevice with the Fishbone. You can also swim to the right of the skeleton piece that drops, but it's slower. Notice that while swimming up to it, Kirby doesn't need to slow down, even when the Fishbone attacks. After grabbing the shard, you can fit in three fires before reaching the exit.