A whole lot of 'em.
Air stall is a (probably unintended) action done by pressing Down+A in the air. It effectively starts a slide for 1 frame: it moves Zook forward 2 pixels, puts him in dash speed horizontally, and resets Y velocity to 0 (hence "stall"). Combining the two-pixel forward boost with regular moving forward, it's possible to reach faster horizontal speeds than intended by air stalling every other frame, leading to a horizontal movement oscillating between 2px/frame and 4px/frame every frame. Naturally, this is abused everywhere in the run. This also causes Zook to move ahead of the camera, which leads to many more glitches.
Getting Zook close enough to the edge (or outside) of the camera/screen bounds causes terrain collision and object collision to wrap and mess up completely. In certain cases, this allows Zook to pass through walls, floors and ceilings, or to ignore enemies that would otherwise harm him (although he can instead be hit by enemies on the other side of the screen).
Getting Zook outside the screen also can lead to a few more glitches:
Anyone who ever played half a stage of this game will know that the minibosses are by far the hardest part of the game, as they have tons of hit points and have damaging and hard to dodge attacks. They are also in every primary stage, except for the Bird stage. Conveniently, this run does not meet a single one of them - this is because the trigger to load the boss, which is normally hit right before entering the miniboss room, can be skipped past by being far enough off the right side of the screen. In combination with the room skip glitch below, the miniboss room itself is also skipped a few times, making it seem as if there isn't a miniboss in the stage at all.
When entering a 1-screen wide room from the left or right, with the next room entrance the same way, it is possible to skip to the next room right away by moving more than 2 pixels horizontally while entering the room (by using e.g. air stall or a well-timed slide). Due to the requirements of the rooms in order to pull off the glitch, it can't be done in every stage. Most of the time, it can be used to skip the miniboss rooms entirely.
If this is done when entering a long horizontal room, it will not skip the room, but instead a graphical glitch occurs where some graphic columns are offset wrongly, causing graphical glitches throughout the room.
A severe glitch which tends to crash and reset the game, and for that reason, it is unused in this run (although there might be possible uses for it found later). Entering an upwards ladder and reaching the top of the screen, the screen will always scroll upwards no matter where the camera actually is. If it is not where it is expected to be (for instance, using the screen out-of-bound tricks so you're far enough to the right that the screen has not entirely scrolled to the rightmost part of a room yet), the screen won't scroll to the next room, but instead to a glitched room where all kinds of random effects may happen.
Sometimes, nothing happens and Zook is transported to one of the first rooms of the stage. Sometimes, a graphical glitch occurs (usually with interface graphics overtaking the room) but otherwise nothing happens. Sometimes the game simply freezes. Most of the time, though, the game will crash and reset itself. After resetting, the tileset usually will be glitched (turning into either garbage, or sometimes all-black or all-white colors). However, so far, no useful applications are known yet.
If the last weapon fired was a charged shot, it is often possible to get an instant charge, simply by charging the weapon without firing a shot. This can be done in a few different ways, such as starting holding the charge button when in the pause menu, while the screen is scrolling, when using movement that inhibits shooting (such as air stall, slides or walljumps), or just while a previous charged shot is still on screen. This is useful whenever a charged weapon shot is needed quickly.
This run uses a different ROM revision than the other run. The ROM I use for this run is mostly normal, except it introduces this glitch. During boss battles, collision detection on enemy attacks is completely messed up and attacks usually just hit random parts of the screen, or in a few instances, hit the entire screen. Because of this, sometimes I need to take damage in bossfights order to be able to hit the bosses fast enough. Other times, I can just phase through all kinds of attacks unharmed.
This is another ROM revision-specific bug, but this time, it is the other ROM used that has it. It is not so much a glitch that is executed or triggered, than it is a simple fact that the ROM revision that has this glitch has bugged SRAM that causes it to think the game is completed and all items are collected from the start, as well as some checkpoints are marked, which allows finishing the game in 25 seconds by just going to the final checkpoint of the final stage and defeating the final boss. However, without this bug available in the ROM revision I use, we have to go the long way instead.
Trivia: the ROM with the save glitch has a mostly different soundtrack. This is because that ROM uses the soundtrack from this game's predecessor Zook Z. The ROM used in this run uses the actual game soundtrack.
With certain precise movement, and seemingly only possible in certain locations, it is possible to wedge Zook into a wall in a standing position. In this situation, jumping up causes Zook to zip 16 pixels upwards. At its fastest, this can be done once every 3 frames and allow for fast upwards zipping. It can also be used to go through ceilings when applicable.
- Downwards ladder entrance
By walking or dashing (not sliding) towards a ladder below the feet of Zook coming from the left side, it is possible to start climbing down 16 pixels to the left of the actual ladder, which can be used to clip movement forward or to go down faster. Similarly, it is also possible to do the same while moving to the left coming from the ladder, but in this case it is only useful as a short 16-pixel horizontal zip.
There is one specific glitch with spike walls: they do not touch Zook if Zook is in either of the first two frames of his wall jump. This means that as long as he is autofiring wall jumps, he can go through spike walls unharmed. This is abused in one section during the first run through Plasma's stage. It looks really silly.
Like how the spike wall can be wall jumped through, it can also be slid through. This allows for an unintended shortcut near the end of the final stage.
- Final boss movement glitch
For some reason I haven't figured out yet, sometimes the final boss
NOT SIGMA has a messed up move pattern which is basically horizontally offset half a screen, causing him to wrap from one side of the screen to the other while moving around. It doesn't have that much impact on the run, though.
- Final boss second phase skip
When the final boss
NOT SIGMA enters its second phase, on the first frame it can be hit, its hitbox and hit pointsare not initialized yet, which means hit points are zero and its hitbox is where the first phase was defeated. Thus, by hitting the boss on that position at the first frame of the second phase, the boss is instantly defeated.
Using this glitch and the charged Ice weapon, it's possible to end input early by just holding out the charged ice over the area where the first phase was defeated, and then ending input.
The leg upgrade, which enabled the airdash, has a few movement glitches that come with it. Most of these involve cancelling air dashes into other things.
Cancelling an air dash (either horizontal or vertical) into a slide triggers an air slide. The air slide cannot be cancelled except by hitting a wall or enemy, or waiting until its timer runs out. It's not possible to jump or shoot out of the air slide.
Cancelling an upward airdash into a horizontal airdash triggers a glitched horizontal airdash which, if no horizontal direction is pressed, remains suspended in air in the airdash animation. The only way to exit is is to either air slide, hit a wall or enemy, or move left or right (with air dash motion/speed) until the timer runs out (which only runs while moving left or right). This has no practical application, but is used during some bossfights for fun.
This is executed by releasing a charged Ice shot in the middle of an upward airdash. This causes Zook to stand in mid-air. Attempting to move causes him to fall down again.
Cancelling an upward air dash into climbing a ladder causes a glitched ladder climbing state, which acts like normal except it cannot be jumped out of. Most of the time this is just a nuisance and is generally avoided.