As the working world shifts from bragging about sleeping so little to realizing the importance of sleep for productivity, a startup called Casper is working to improve the bed you sleep on, Mashable reports.

Casper, a New York-based startup aiming to reinvent both the mattress and the mattress shopping experience, announced Thursday that it has raised $13.1 million in Series A funding led by New Enterprise Associates and with participation from SV Angel and Ashton Kutcher’s A-Grade Investments. Investor demand came as somewhat of a surprise to the founders at Casper, which had raised a modest $1.85 million seed round in March.

“We were very much surprised by the demand,” Philip Krim, cofounder and CEO of Casper, toldMashable. “When we launched the business on April 22, we had no idea and no plans to do fundraising.” What changed, according to Krim, was the company’s degree of success with the launch.

Casper topped $1 million in sales after just 28 days and has done “millions” in sales to date.

Krim and his team worked to simplify the process of buying a mattress. Casper develops and sells just one mattress — The Casper — in six sizes starting at $500. Shoppers can order the mattress online and have it delivered in a box the size of a mini-fridge in five days or less. You then have up to 40 days to try out the mattress and return it for free.