since this post blew up, i've been wanting to do an addition with all of the recommendations from the comments and tags. but there's a lot of them. some people might be crazy enough to sit down and seriously put them all in one post with descriptions. those people are honestly sick in the head.
anyway, here's all of the recommendations from the reblogs. not all of them are text-based, but it's a great mixture of styles. also don't forget the links in the second paragraph of the OP which will take you to FMHY where there are a bunch more games listed.
A Dark Room - text-based science fiction role-playing game.
corru.observer - science fiction adventure web game.
Improbable Island - old-school text adventure game.
Candy Box 2 - incremental clicker game that evolves into RPG.
Arcanum - open source wizard clicker game.
sandspiel, Powder Game, Powder Game 2, The Powder Toy - more sand physics games.
Orb.Farm - fishtank simulator.
Façade - experimental game with a real-time interactive narrative where you try to fix a failing marriage.
The Catacombs of Solaris - trippy art game.
Yume Nikki Online - online version of the surreal classic plus fangames.
The Barncle Goose Experiment - combine element/alchemy game based on antique theories of abiogenesis.
Fallen London - free-to-play text-based open world RPG.
Nested - very unique text-based universe expanding game. described as possibly @orteil42's favorite thing he's ever made.
The Process of Elimination - interactive web novel (by @hypertextdog)
Discworld MUD - multiplayer, text-based, online game (a MUD, or text MMORPG) based on the Discworld books.
Horse Master - surreal text game about training a horse.
EYEZMAZE - flash (RIP) or HTML5-based puzzle games.
You Are Jeff Bezos - text game. spend Jeff Bezos' fortune.
The Password Game - challenging puzzle game where you have to meet password requirements (by neal)
Universal Paperclips - incremental paperclip making game.
Half-Earth - planetary disaster planning game where you try to save the world using socialism.
ChooseYourStory - community-driven website centered on CYOA style story games.
PhD Simulator - random event based text game. make your choice each month and see if you can graduate on time.
Dungeon Crawl Stone Soup - open source roguelike.
Cataclysm: Dark Days Ahead - turn-based survival roguelike set in the modern day.
Nethack - open source roguelike originally released in 1987.
FarmRPG - simple, mobile-friendly, text-based farming RPG.
Kingdom of Loathing - browser-based community MMORPG.
PokeRogue - browser-based Pokemon roguelike
Text Game Builder - works in your browser, with just a little bit of Python (by @grumpygandalf)
Twine - great (free!) tool for making text-based games quickly.
Ink - scripting language for interactive fiction (also free)
Flashpoint Archive - a community effort to preserve games and animations from the web.
PICO-8 - fantasy console for making, sharing and playing tiny games and other computer programs.
Library of Babel - interactive illustration which attempts to simulate what it might be like to browse The Library of Babel.
Superbad - technically not a game, sprawling website full of secrets.
17776 - serialized speculative fiction multimedia narrative about football in the far-future. beautiful, creative, legendary. created by Jon Bois, a legend and one of my favorite writers of all time.
Choice of Games - text-based, choose-your-own-adventure games (interactive fiction). some free-to-play, others can be bought like an ebook.
The Deep Sea - scroll to the bottom of the ocean. encounter the humble squid and his friends (by neal)
Space Elevator - like The Deep Sea, but up instead of down. you can equip your avatar with a scarf (by neal)
Internet Artifacts - an interactive history of the early internet (by neal)
If The Moon Were Only One Pixel - scroll through an accurately scaled model of the universe.
r/incremental_games - reddit community for incremental games.
r/WebGames - reddit community for web games in general.
thank you to everyone who contributed and the creators. please be sure to show them some love where possible.
discoholicmusic
ellievsbear
kianamaiart
andulkaphoto
