10 Missile Zebetite Kill
It is possible to kill all Zebetites except the first using precisely 10 missiles.
Zebetites have exactly 1000 health, and missiles deal 100 damage. Usually, Zebetites gain health for every frame they are on screen. Thus, one would initially expect this is impossible: Even if the Zebetites are manipulated to be on screen for as little as possible, they will still be on screen for some finite amount of time. However, Zebetites do not gain health for 5 frames after damage has been dealt. Thus, if a Zebetite is moved on screen for fewer than 5 frames, its health will never increase.
Therefore, by carefully manipulating the screen position, it is possible to: (1) Fire a missile while the Zebetite is off-screen, (2) move the Zebetite on screen for fewer than five frames while the missile hits; (3) repeat with remaining missiles.
Current best PAL setup
The current best RTA setup is as follows:
This is on PAL. You can get this setup to work on NTSC by dancing on the pillar you jump right onto, but then the turrets have a lot of time to shoot you so it's pretty RNG dependent.
The setup is as follows:
(1) Initially moonwalk left to scroll the screen as much as possible. I am unsure how much this is required, but it does move the left turret off screen which helps.
(2) Make sure the Rinkas are in a favorable position. Shooting the bottom then the top as quickly as possible works.
(3) Run into bottom Rinka just before it hits you.
(4) Quickly perform a full jump into the ceiling. Keep holding right as you go under ceiling, but release right before landing (so your position is normalized).
(5) Buffer jump back left, while you still have i-frames (i.e., still be holding jump).
(6) Do a tiny jump and turn back right. The turn-around must be done in the air. The jump should be tiny to avoid the turret.
(7) Crouch and shoot the bottom Rinka.
(8) Turn around, shoot a missile, jump, and turn-around in the air. The air turn-around is a 4 frame window. This is the hardest part, as the turret shots can snipe your missiles. If you suspect they will, then turn back right and get the Rinkas lined up (shooting bottom then top quickly) and try again.
(9) Moonwalk the camera back into position. Do not moonwalk to far left, since then the left turret can hit you. Repeat steps as needed.
Note getting hit by the Rinka takes 220 damage, if going for the double kill (and you have Varia but not Gravity). This means you either need two Energy Tanks for this setup, or you need to use some reserve health. Getting hit by the Rinka is not actually necessary, so you could skip it. But then on the jump over and back, you can get hit by turret shots. So it is more dangerous to skip it.
It should be noted that getting hit by the Rinka is not actually necessary for this strat. With the Rinkas well-positioned, you can simply jump over them and then jump back. If you do this, there is a chance of getting sniped by a turret shot. That's the purpose of the i-frames. If you want to run 1+2 Energy+Reserve Tanks, then you could do the first couple of missiles without taking damage and then switch over.
With this setup, if you get hit by a Rinka or a turret shot in the initial stages (e.g., after you have moonwalked the camera but before jumping), the setup may not die. So you could choose to continue.
However, if you mess up the first jump, you will be far to the right. It will be difficult to get back left without accidentally moving the zebetite on screen. It is possible by carefully moonwalking left and jumping over the pit cautiously. This is difficult to do with the Rinkas shooting at you, so this will usually result in failure.
Current best NTSC setup
Due to differences in movement, the above setup doesn't quite work on NTSC. The following setup is the easiet method currently found for NTSC:
See the description of the above clip for detailed steps.
The above setup works on all Zebetites.
However, the second and third Zebetite can be double killed. This is accomplished by hitting the second Zebetite after it has died, but before it has exploded. What you hit the Zebetite with can be any projectile: In particular, it can be a beamshot.
Thus, while killing the second Zebetite, you should repeat the setup for an eleventh shot of a beamshot. This will then kill both Zebetite 2 and 3.
The first Zebetite cannot be moved off screen, so cannot be killed in 10 missiles.
First and last shot of the kill
In theory, the first and last shot would not need the full setup.
For the first shot, it doesn't matter if the Zebetite is on screen beforehand. Thus, in theory, one can fire the missile with it on screen, and then quickly move it off screen. A setup would have to be developed.
For the last shot, it doesn't matter if the Zebetite is on screen afterwards. Thus, in theory, one can fire the shot with it off screen, and then just run to put it on screen as the shot would hit. It was attempted to find a good setup for this with a beamshot (for the double kill), and it seemed to fail more often than the complete setup. However, this could simply be due to improper timing.