In 2015, Microsoft bought Christian Reber’s to-do list app, Wunderlist, for a sum that was reported to be between $100 million and $200 million.

It was a significant amount of money and a huge moment in Reber’s life but it didn’t leave him feeling as one might expect.

“I think selling Wunderlist was a bizarre experience for me,” the Berlin-based entrepreneur told CNBC.

“I felt like I lost a child in a way and as a father of two, I feel like I can say that,” he added. “I really felt like I got depressed. I felt really unhappy.”

Wunderlist was a simple app that amassed around 16 million users in its lifetime. One of its biggest selling points at the time was that users could access it on their phone as well as their computer.

It was a big part of Reber’s life and selling it wasn’t easy.

“I felt like I totally disconnected from my team and from the company that I’d created,” he said.

When asked to further explain his feelings at that time, Reber replied: “You should ask my therapist.”

Reber now believes he wasn’t mentally prepared to sell Wunderlist, which he had been trying to make as big as possible for five years.

“Selling it all of the sudden felt completely unintuitive,” he said.

When Microsoft came knocking with the offer, Reber’s partner, Charlette Prevot, was pregnant. Prevot co-founded Wunderlist with Reber and four others.

“The choice I had to make as a founder was I either raised a growth round and tried to turn this into a profitable business, or I sell this for a very profitable amount of money and my family gets independence.”

Reber and Prevot eventually decided to step off the start-up rollercoaster, which had almost seen their business crash and burn on several occasions.

“I was completely burnt out and I was tired and I felt like it was the best decision for everyone involved to sell the company,” Reber said, adding that he had to put on a “poker face” as he did it.

“When I sold it I never celebrated it, I didn’t party, didn’t go for fancy dinners. I just like muted every email and felt like I was sad. I’m not even joking. There were moments where I was holding my child and I asked my wife to take him because I felt so sad that I didn’t want him to see daddy being sad.”

Reber said it took him a year or two to start to come to terms with the sale.

“I got financially independent, which is awesome,” he said. “I built something that had a really positive impact. People will always remember Wunderlist. It was a great product and lots of great people got amazing jobs at Microsoft. So there’s really no reason to be frustrated about it.”

What happened to Wunderlist a few years after Reber sold it was still hard for him to stomach.

In 2019, Microsoft announced it planned to shut down Wunderlist and replace it with Microsoft To Do.

In September of that year, Reber made a bid to buy the app he’d invested so much of his time in back from Microsoft.

“Still sad Microsoft wants to shut down Wunderlist, even though people still love and use it,” Reber wrote on Twitter in Sept. 2019.

“Please let me buy it back,” he added, directing his plea straight to Microsoft CEO Satya Nadella and Marcus Ash, vice president of product and engineering at Microsoft.

His bid was unsuccessful and Microsoft pulled the plug on Wunderlist in 2020.

Reber wasn’t ready to give up, however.

In 2021, he founded a new to-do list app called Superlist, which he describes as the “unofficial successor to Wunderlist.”

One of the main reasons Reber felt frustrated when Microsoft shut down Wunderlist was because he felt that the app never became the product he wanted to build.

“What we wanted to do was build the de facto standard application to collaborate on personal projects and in business,” he said.

There are either enterprise products like Asana and Trello or personal to-do list apps like Things or To Do.

“I feel like nothing really nailed the bridge between both,” Reber said. “You either get like very cluttered software that is basically optimized for project managers, or you get like these very personal to-do apps that make it impossible to collaborate.”

Superlist is intended to be the “perfect bridge” between personal to-do apps and enterprise collaboration software. It’s designed to help users scale a project from one person to 100 or 200 people.

So far, the company employs around 20 people and has raised $3 million, with another funding round coming soon.

“I am dreaming of building my own Salesforce, my own Microsoft, my own Atlassian,” Reber said. “That’s really what’s driving me.”

He doesn’t have all his eggs in one basket though. Reber has co-founded another company called Pitch, which competes with Microsoft’s PowerPoint.

“The reason we started this company is because we felt like presentations as a medium are really driving the world and influence the biggest decisions in business and politics,” Reber said.

He added: “Think of it as like PowerPoint combined with SlideShare and Docs.”

The four-year-old business, which employs around 160 people, has raised a little over $130 million and it was most recently valued at $600 million.

“I think it’s incredibly easy to raise funding for technology companies right now because it’s like there’s more money than companies on the market,” Reber said. “As a founder who is starting companies more frequently, I feel like it’s never been better to raise.”