What's different from vanilla

Seeded luck, loot minimums, world generation and Nether changes.

Tascade changes a few things about Minecraft 1.16.1 so that races are fair and seeds are fun. Almost all of it comes down to two ideas:

Same seed, same luck. If you and your opponent do the same thing, you get the same result. No more losing a match because their piglins were nicer to them.
Fewer dead seeds. Every seed should give you a real shot at a good run.

These changes only apply to worlds Tascade creates for runs. Any other world you make plays exactly like vanilla.

Heads up: because of all this, Tascade is not a legal mod for speedrun.com and never will be. It's for fun and practice. Please don't use it for runs you plan to submit!

World settings

Difficulty is Easy. Peaceful isn't allowed, since it would refill your hunger and clear out hostile mobs. If you switch to Peaceful in the options while paused, the world goes to Hard as soon as you unpause, and /difficulty peaceful simply refuses.
Cheats are off, unless you turn on Allow Cheats in the settings. Runs with cheats are unrated.
/seed doesn't exist. Both players race the same seed, so knowing it would let someone look the world up in a seed map.
Your spawn point is fixed. The seed filter picks the exact spawn, and there's no random spawn radius. If a tree grew right where you'd spawn, you're moved up to 6 blocks to the nearest clear spot. Respawning without a bed puts you back on that same spot.
The Nether has its own seed, separate from the Overworld's. That's what lets Tascade pair a great Overworld with a great Nether. See How the seed filter works for more.

Same luck for everyone

In vanilla, a lot of randomness comes from one shared random number generator, so two players on the same seed get different results as soon as they do anything slightly differently. Tascade gives each kind of random event its own sequence, fixed by the seed.

The key idea is that your count is what matters. Your 4th blaze kill drops the same thing as your opponent's 4th blaze kill, even if they got there faster or killed some other mobs along the way.

What	How it works in Tascade
Piglin barters	Your 1st barter, 2nd barter and so on are the same as everyone else's on that seed.
Mob drops	Your n-th kill of each mob type drops the same items, with the same looting bonus, gear and experience. Only kills you get credit for count, so a zombie burning in the sun doesn't change anything.
Block drops	Your n-th mined block of each kind drops the same thing. Your 10th gravel either gives flint for both of you or for neither. Fortune and Silk Touch work as normal. Only blocks you mine count, not explosions or water.
Eyes of ender	Your n-th throw breaks or drops just like everyone else's, at vanilla's 1 in 5 break chance. Your 2nd throw never breaks.
Mob spawns	Each chunk's spawns, each spawner's spawns and the mobs that come with structures (like bastion piglins) are seeded. Whether a mob actually spawns still depends on light, the mob cap and where you're standing, just like vanilla.
Structure chests	Bastion and desert temple chests roll their loot from the seed and their position, so they're the same in every world on that seed, whenever you open them.
Ender dragon	The dragon aims at most 15 blocks above its path nodes instead of vanilla's 20 (matching MCSR Ranked), and those heights come in the same order on every world with that seed.

Guaranteed barters

Your first 140 piglin barters are planned ahead so they always add up to at least:

3 Fire Resistance potions
15 obsidian
64 string
30 ender pearls

Barters after the first 140 are regular rolls (still in the same order for everyone).

Loot minimums

Some chests get a small top-up when the roll comes out short. A lucky or average chest holds exactly its vanilla loot. Only an unlucky one gets a bit extra.

Chest	At least
Buried treasure	7 iron ingots, 2 gold ingots, 4 cooked fish
Shipwreck treasure	7 iron ingots, 2 gold ingots
Shipwreck supply	3 carrots, 6 wheat
Village armorer, toolsmith and weaponsmith	4 iron ingots, 2 gold ingots, 2 apples
Ruined portal	A flint and steel (or fire charge), 3 iron ingots
Desert temple (all four chests together)	7 iron ingots, 2 gold ingots
Bastion (all chests together)	5 obsidian, 6 iron ingots

Between the bastion's chests and the guaranteed barters, a fully looted bastion gives you at least 20 obsidian.

Iron golems also always drop exactly 4 iron ingots, instead of vanilla's 3 to 5.

World generation

Lava pools near villages and desert temples. These seeds get 3 small lava lakes (about 7 to 10 blocks wide and 2 deep) 48 to 96 blocks from the structure. They're placed after the world has finished decorating itself, and they step aside if a pond or tree is in the way.
No crying obsidian in ruined portal frames. Any crying obsidian that lands in a frame slot becomes regular obsidian, so the frame can always be finished.
A clean pie chart for buried treasure and shipwrecks. On these seeds, no other chest or spawner structures (villages, temples, ruined portals, ocean ruins, mineshafts and so on) or dungeons generate within 128 blocks of the intended structure and your spawn. That way the F3 pie chart only points at the chest you're looking for. Strongholds are never touched.

The Nether

A fixed entry point. The first time you go to the Nether, you land at the seed's entry portal, wherever you built your Overworld portal. It's always 48 to 96 blocks from a bastion and faces toward it, in a clear pocket with solid ground. Any later trip that wouldn't link to an existing Nether portal lands there too. Going back through the entry portal returns you to the Overworld portal you last came through.
Coming back out on the surface. In vanilla, a portal built high in the Nether often spits you out in a cave. In Tascade, a Nether portal at y 50 or higher gets its Overworld portal on dry ground at the surface (or floating on a small platform at y 70 or above if you're over open ocean, like vanilla). Portals below y 50 work like vanilla, so building at y 30 to 42 to come out inside the stronghold still works.
Calm zombified piglins stay out of bastions. None spawn inside or on top of one, and wandering never takes them in. If you make one angry, it'll still chase you in like normal.

Interface changes

Race HUD on the right side of the screen during a run, and run info in the Tab list.
Match chat: in ranked, what you type in chat goes to your opponent.
Pause menu: "Open to LAN" is replaced with run controls (change seed, offer a draw). In ranked, the quit button becomes Forfeit Match.
End of run: you're switched to spectator, the result appears as a title for a few seconds, and then the results screen fades in.
Loading screens show the seed type's picture and your opponent, and in ranked the world generation screen shows how far along your opponent's world is.

Want the full picture of how matches, pp and Elo work? Head over to How Tascade works.