The categories TDO Glitchless† and Any% Twin Galaxies Rules are so-called glitchless categories. This post details exactly what is banned in these categories and why. It also gives examples of speed tech, including "glitches" and manipulations that are not banned and why. My hope is that this will give a foundation for the spirit of these categories both for present understanding and deciding on future discoveries.
NOT ALLOWED IN GLITCHLESS: Block Clips/Screen Scrolls Key Door Glitches Bait Storage Wrong Warps Arbitrary Code Execution, Save Corruption, Memory Corruption, Hardware Manipulation, etc.
Descriptions of tricks and glitches, and reasons for (dis)allowing.
Block clips/Screen scrolls The technique which allows the player to break through 1-pixel thick boundaries and do sequence breaks both small and large. It's easy to mindlessly clip when used to doing them in runs. If you clip through a boundary, immediately turn around and exit through the same boundary, or the run must be rejected. Being hit by enemies can also cause you to clip through boundaries. Your run won't automatically be rejected for something out of your control. If one happens in a submitted run, please bring it to the moderators' attention. Clips are disallowed because the game's obstacles have boundaries to prevent the player from passing through them and trivializing encounters.
Key Door Glitches The first practical example is re-entering Level-1 in first quest to pop the top lock. Another is known as "Khananakey" -- it is possible to walk through key doors without a key while a shutter door or bomb wall is opening. This is not allowed because doors are meant to stop players who don't have keys.
Bait Storage Using Up&A when giving a hungry goriya gatekeeper the Bait/Food to clear the gatekeeper and keep the Bait. In gameplay, the Bait is a useful item that can be repeatedly used to corral enemy Goriyas (and other monsters!) without being consumed. Giving up your Bait to the hungry Goriya is a sacrifice of a useful item in order to progress. From a role play perspective, the Goriya cannot have its hunger satisfied if you still have the meat. Be the hero, let the hungry Goriya have its meal.
Wrong Warps, such as Roocorder The only known wrong warp that does not have a boundary clip as a prerequisite is Roocorder, which is riding a warp wind across a dock to launch the raft creating new warp destinations. Other known overworld wrong warps simply take the player back to the starting screen.
All other known glitches and manipulations are currently allowed in Glitchless. New discoveries will be considered after exploration of the costs and benefits and how they fit with the design of a category.† If you're wondering why a trick or glitch is allowed or think that it should be banned, please consider the following. Some glitches are unavoidable. Some have negligible benefits which may come at a price, or have no benefit at all. Sometimes a glitch or a manipulation may improve the reliability of an outcome, but not change what is possible. On the other hand, the effort of avoiding glitches can force the player into taking slower paths or higher risks simply for the sake of avoiding a bug.
Take the Master Goriya room in Level-2 for example. If you defeat the master while boomerangs are flying, when the boomerang returns to a dropped item it will change into a bomb. Banning this would force the player to one of these solutions: risk nothing, kill the master last; be cautious, kill the master when no boomerangs are flying; be careless, reset when glitches happen; avoid fighting them completely.
Let's weigh the quantifiable the benefits of the glitch. Without the glitch, the player already has a blind 52.7% chance of getting at least one bomb (barring bad PRNG distributions or unknown glitches affecting the drops). Global count manipulation increases the drop chance to 64.8%. In the unlikely scenario that five boomerangs return to dead Goriyas, another item will change into a bomb 83% of the time.
The boomerang glitch doesn't create a previously unavailable routing opportunity or break a sequence, it merely improves the efficacy of an action that would be taken regardless of the glitch existing. So we allow it, and other glitches based on similar reasoning.
Green gleeok head's 3/8 heart damage is another allowed beneficial glitch.
Object timer manipulations, e.g.: Tooting after waking an Armos; placing a bomb before tooting vs. Digdogger; tooting after touching a bubble; tooting during the Gannon fight.
PRNG manipulations are allowed. Gannon "stun lock" is a manipulation of Gannon's Left vs. Right respawn RNG and the fixed duration of his invincibility. Standing in the middle of a room to attract enemies toward you is in fact a PRNG manip. During pauses and game-initiated freezes (recorder toots, medicine chugs, item hoists) some timers with fixed or randomly assigned values controlling enemy actions continue to run. Money Making Game runs on PRNG -- results can be predicted and manipulated.
The way enemies are counted is limited to number and not type. Partially clearing enemies in a room and re-entering will change the enemy type. You can also despawn a boss by half-clearing it and re-entering.
† A more accurate category name given the rules would be "Numerical Level Order, Limited Sequence Breaks". The category was called Traditional Dungeon Order because some of its progenitors saw the it as a way to play the game similarly to how they did as a child. As a point of fact, the game is open world and different people had different ways to beat the game, including going to Level-2 first. Having 'Traditional' in the name was not meant to imply that playing the game differently was wrong in some way. If every individual in the community were to ban anything they didn't know as a kid, the category likely would allow practically nothing.
