100% Route
Note: this page was adapted from swordsmankirby's guide. Some strats may be outdated.
1-1
Despite being the first level, there are some tricky parts, and it's relatively dense with enemies for a single fire section.
Grab single fire on the first Bobo. The closer you are to the enemy when you start inhaling, the quicker it goes into your mouth. After getting the powerup, there are lots of enemies at different heights before you see Shard 1. The clip shows the route most people use, which involves floating up to the top of the screen.
The N-Z miniboss is the only enemy that takes three hits to kill. To not get hit by the first normal-sized N-Z that spawns, you can take a step forward before doing the first fire. Another strat involves jumping, the idea being that recovering is faster if you hit the enemy from higher up, at the cost of taking the time to jump. I believe jumping saves a little bit of time, but you risk jumping over the miniboss.
After single firing past several shotzos, there is a Poppy Bros. enemy to combine for fireworks. Throwing the powerup in front of him is the fastest, while going behind him is safer. A nice backup if you take damage on a Bronto Burt is to let the bomb hit you and knock the powerup out of you.
Shard 2 is underneath a bomb block, and since there's water around it, fireworks is useful for minimizing the time spent in it. Note that attacking the Bouncy after getting fireworks is often not necessary if you're at the right part of its jump cycle. The Waddle Dee fight is straightforward. Since the fireworks hitbox lasts for awhile, it's easy to anticipate when Waddle Dee becomes vulnerable. After four hits, throw the powerup for two damage for the kill. Float up after grabbing Shard 3 so that Ribbon goes back into Kirby faster and the fadeout gets triggered sooner.
1-2
A level where lots of single fire is required and some RNG comes into play.
For the Poppy Bros. enemy, it's better to just play it safe. The fast fire strat is awkward at first, but not really that precise.
After single firing all the way across the rest of the first room, climb the platforms in the second room. Doing a fire on the ground and jumping into the first platform is faster, but getting the spacing right is tricky. In the next room, forget about Waddle Dee and drop into the abyss for Shard 1 (middle). My visual cue for starting the fire is when Kirby tumbles into his nosedive animation.
The Bouncy miniboss drops Shard 2 in the middle of the room, so graze over it with single fire and do three fires from the other side. The visual cue for the right height is one of the platforms in the background, but this trick is really generous to begin with. The puff after the first fire is optional, and it's even possible to get two hits before hitting the ground with this strat.
Adeleine first draws five enemies in a row. Kill each of them quickly, but make sure the fifth one is done as early as possible. When she draws the Ice Dragon, stand on its right. If it doesn't turn around, it'll jump across the screen (top-right). Otherwise, it'll drop an ice cube (bottom-left). Dark Matter and Adeleine after are straightforward (bottom-right), though the former has two patterns that behave similarly to the Ice Dragon. Grab Shard 3 in the same way as in the previous level. In between phases, Adeleine can randomly wave her paintbrush, delaying her next drawing.
1-3
After 1-2, you should have the fire powerup. Since there are a lot of enemies, most of this room is done on the ground. The Skud enemy sitting on the block is in a position such that if you do two fires from the start, it'll land on you, so I take a little step after the first fire. In the next room, it's easiest just to fire up the stairs.
When going upwards, it's faster to jump on the platforms, instead of climbing from underneath them or floating up. In real time, it's hard to jump on all the platforms, so you would climb underneath one of them (left). In the next room, you combine for double cutter, and swallowing the powerup while falling through the loading zone saves a bit of time (middle).
There is a small window for using double cutter and not hitting the platform before getting Shard 1. Right before going through the loading zone, you can remove the powerup by putting it directly in your mouth. I like to face left when using the powerup, because if I use it too early, it takes a shorter amount of time to come back to Kirby for some reason.
After passing through the Adeleine room, there is Shard 2 behind you. To shortcut the whole room, you can float up near the Ghost Knight to go directly to the exit. Combine for double fire for the next two boss fights.
Dedede is straightforward, but note when he becomes vulnerable, using the health bar as a visual cue. There is an RNG-dependent strat which involves hoping Dedede jumps in the air with his hammer on the first phase, causing him to enter his second phase faster, but this is really unreliable.