Movement

Coming to this game, the most immediately noticeable feature of the game is that movement is not like a Mario game. Turning around takes time. Ducking takes time. Jumping and moving aren't possible while ducking. Turning around isn't possible while attacking.

However there is a way to turn around quickly, and that is to jump in the direction you want to turn toward. That avoids the turning around animation, but obviously it also means you have to jump in that direction. It's useful in a speed run, but must be applied with practice.

Treasure Chests and Upgrades

All item drops in the game come from treasure chests which must be attacked to open. Some items give one-shot boots (temporary invincibility gem, one-heart small life refill, three-heart large life refill, and a 1-up). Others give a 'permanent' upgrade that lasts until the end of the stage, or until death, whichever comes first. This includes the wing boots (see Jumping below), the sword (see Attacking below), and extra heart containers (see Life and damage below).

Treasure chests only respawn on death.

Life and damage

You start with a life bar of three hearts. It can grow as high as five. Even if you pick up a third additional heart container, it will just refill one heart, and not extend the bar to six hearts.

Jumping

The game gives you a double jump when you acquire the wing boots. However you can only use the double jump while you're still moving upward. If you're coming back down from your jump, the double jump will not function.

There is one [frame and pixel perfect jump] in 6-2. It was not done in the Hotarubi 9:27 run, but it has been done in live runs by StuckInAPlate. Here are a few key frames from the [8:19 TAS]:

This is frame 24306 of the 8:19.05 TAS. We’ll call this frame zero. It is the first frame Riki is visible on this screen. The controller is holding Right.

This is frame 3. Three frames later, A is pressed, while Right is still held.

This is frame 12. Nine frames later, A is released, while Right is still held..

This is frame 21. Nine frames later, Right is released, and Up is pressed.

This is frame 22. On the next frame, Up is released. The controller is neutral.

Attacking

The base weapon you start with has little range. However an upgraded sword can be acquired. This extends range.

When you have one heart of life left, jump attacks will do additional damage, up to three hearts' worth on bosses. However the attack is cut short if you do your double jump before the full damage is done.

Death glitch

By dying after a boss finishes exploding, and pressing start, the end of stage fadeout can be forced to happen faster. This should not actually cost a life, though.