Instead of the highest tier door winning you the game, it teleports you to the 0,0 of floor 3 -- you can go back to where you were before easily.
This space has %2=0 doors arranged in a grid with doors blocking nodes. Teleport doesn't work down here. Door colors are random but prefer higher-tier keys. Distribution is seed specific.
The bg could maybe change on move, to make this region more interesting.
There are also exits that go to other parts of the endgame.
Somewhere in the endgame is the item that wins you the game.
time items only decrease it by 20 seconds or so.
There should be a db high scores table for winning a seed. Scoring should be based mostly on time but grant bonuses for keys and raws, with the distribution here being seed-specific.
This game should have some pretty extensive dodecaverse lore that maybe also ties into shatterloop lore.
Lore books are scattered throughout the phonemaze. The starting room has one that tells you how to play, getting there should be intuitive and also exits won't appear until you grab it.
Each lore book will repeat the previous piece of lore and let you choose a new piece of lore that builds on it. This should expand out but also braid together in a mazelike way and then also link back to the beginning.
Beating a seed will let you get a single big piece of lore that kinda ties together all the little lore. There's way more choices here.