The Treasure At The End Of This Dungeon is a lyric game about roguelike dungeon crawls. Don't go in expecting something extremely concrete and runnable. But do go in expecting some spectacular writing, and the execution of a concept that hits harder than any other dungeon crawl I've ever seen.
Treasure At The End's PDF is 16 pages, with a straightforward layout that's well organized and easy to read.
For core mechanics, Treasure At The End is pretty direct. You follow the rules for your character class, and you follow the rules for the dungeon room you are in. Anyone who breaks the rules dies. Anyone who opens the door to two dungeon rooms dies.
The dungeon rooms are simple, and focus on broad, common beats in dungeon crawls. A puzzle, a trap, a fight, etc. And then the loop begins again.
The character classes are much more interesting, and each interact with death-looping in different ways. The Muscle can simply ignore death by crossing rules off of their sheet. The Mage loses spells on death, but gains more casts and the ability to combine their remaining spells. The Thief can bluff new mechanics, but erases everything on death. The Healer can prevent deaths and permanently erase mechanics from rooms.
Overall, if you like lyric games and metafiction and seeing the dungeon crawler formula picked apart into fractals, I'd strongly recommend checking this out. It's playable, but more than that it's a fascinating read.
Also, there is a way out of the dungeon. I think you can find it too.