Making a web game with Ruby

Tonight I sat down to work through a bit more of Learn Ruby the Hard way (seriously, I'm on lesson 47 out of 52, I really should just finish it) but it didn't take long for me to get antsy to work on an actual program. Here's my current idea:

Building on AAN and Skyrim Stories, I want to take the dungeon crawler I made back in the summer, add some "awesome" hand-drawn graphics, and make it playable online. So far I'm picturing this as a Sinatra app, since it's pretty small and I won't need a database, and I can use Yaml for room descriptions. I've thought about ways to display different graphics for rooms when certain events happen, and I need to figure out how to take input from a user when an application is running on the web.

How do you collect information from a user, manipulate it, and trigger other functions based on the input when an application is running on the web? I'm unclear as to what the web equivalent of input = gets.chomp() is.

This project is largely just an excuse to take code I've already written (for the most part, it'll have to be refactored a bit for the web) and get more comfortable with getting a Ruby application to run on the internet. On top of that, I'm big into video games myself, and I'd love to have a hand in making games. Ruby probably isn't the best choice for making a game, but whatever!