You'll forgive Stewart Butterfield if his entrepreneurial résumé seems a bit, well, disjointed.

After co-founding the photo-sharing service Flickr in 2004, Butterfield went to work for Yahoo after the company's 2005 acquisition. He worked at Yahoo until 2008, when he left to found Tiny Speck, ostensibly a mobile gaming studio. Tiny Speck raised about $17 million from notable VCs like Andreessen Horowitz and Accel Partners, and went on to release Glitch, a "massively multiplayer" online game. Unfortunately, the game wasn't "massive" enough.

When Glitch shut down in November 2012, Butterfield had a few options. He could work on another game. He could return his investors' money back to them. Or he could do something completely different.

He chose the latter.

Last week, Butterfield and his team of 11 unveiled Slack, a collaboration app built for the digital age. Butterfield had predicted the app would sign up about 1,000 users in its first week. It signed up 13,000. It's also been pretty much universally acclaimed by critics and it quickly picked up the moniker, "email killer."

You might say Butterfield has managed to turned a glitch into (ahem) gold. 

"I think of myself more as a designer than a serial entrepreneur," Butterfield says. "As a designer, the easiest way to see that something happens is to start a company and then be the boss and then people have to do what you say."

I spoke with Butterfield recently by phone to learn more about his latest act. Here's an edited transcript of our conversation with. 

Tell me a bit about Slack. 
When we first started Glitch, there were four co-founders of the company. We built Flickr, and worked together at Yahoo, and then started Tiny Speck. We were split in Vancouver, New York, and San Francisco. So we used an old chat technology called IRC. Almost nothing went through email. As we grew the company, we had remote workers all over the place. At its peak, we had like 45 people working on the game. We had an illustrator in the middle of Russia. Artists and animators all over the place. And customer service across the United States. Our company server had less than 50 emails.

So we built our own internal communication system. Every hour we would pump stats into IRC. Database alerts, open support tickets, etc.

In the end, we had a very cobbled together system, but very effective. And when we decided to wind down the game, we were thinking about what we wanted to do, and all of us realized we would never want to work without a system like this again. But, it could be made so much better. We thought it would make a great product. It hit a nerve. Our goal was to get 1,000 teams to sign up in the first week. Right now, we're at 13,000.

What did your investors think of the pivot?
We have two board members other than me. One is from Andreessen Horowitz and one from Accel. Those are our biggest investors. Neither of them wanted to see the company shut down. We still had money in the bank. They were enthusiastic about this idea. 

Was it difficult to convince the team to work on an entirely new project?
We went went through a really cathartic change. The shutdown of the game was traumatic. We had 150,000 players, they were heartbroken. We put it all out there. Once we had processed that--I make it sound like a recovery group, or something--the disappointment, the sadness, it was pretty easy to move on. Because I think everyone on the team had recognized what we had built internally in the team. It's a much easier problem to tackle, in a way. A game is either going to work or it's not. And you put in millions of dollars and thousands of hours of work. But at the end of the day it's binary. But with Slack, it's much easier to get feedback on it, to make changes, and move forward inch by inch. 

How do you decide which ideas you want to pursue?
I'm not sure, to be honest. I think I just do whatever is most interesting to me at the time and it works for the people I'm working with, and I can convince other people I'm working with that there's value. 

There are plenty of collaboration apps out there. Why do you think the world needs another one? 
I've been doing this for 15 years. Every 18 months or so, I feel like there's some software that's about to save us--task management, project management, to-do lists, or something like that. Sometimes it's been things that I've worked on myself, as an internal tool for the company. Sometimes it's products that other people come out with. So, Asana comes out and it's like, "Ah! Finally, our problems are solved." Then two weeks later, we stop using it.

There's nothing wrong with those products, but project management software is inherently difficult because in order to build it, you need to have a database schema. That means you have to have some model of what ownernship means, and what priority means, and what a to-do list means. The lucky teams will end up with a tool that fits them well. But most teams suffer with their tool, or abandon it. So we don't want to build project management software. 

What's the future of email?
Using it as a primary means of communication is crazy. It's just the wrong tool. In 10 years, everyone will use some kind of centralized service. We obviously hope it's Slack.