Silicon Valley has been on a tear over the last several years, as young people with big ideas and access to even bigger capital flows have been recklessly blowing that cash (and blowing off steam) in pursuit of the next unicorn. But as funding dries up and valuations plunge, the party appears to be coming to an end.

Zenefits, the high-flying human-resources start-up once valued at $4.5 billion, is feeling the hangover set it. Earlier this month, the company’s C.E.O., Parker Conrad, publicly resigned amid concerns over the company’s regulatory compliance and its frat-like culture. Last week, the California Department of Insurance announced it was investigating the start-up. Under the pressure of the Valley’s hyper-growth environment, Zenefits allegedly let insurance brokers shortchange mandatory requirements that allowed them to obtain a license and join the Zenefits ecosystem more quickly.

Conrad was replaced by David Sacks, who promptly acted to clean up the compliance mess and proceeded to ban alcohol from the office. After a series of Instagram photos posted from the company’s offices and retreats showing rounds of shots and “champagne showers” at pool parties in Las Vegas with the hashtag #friendswithzenefits made waves with investors and the media, Sacks sent a memo to staff saying they would find other ways to socialize and have fun, without booze, according to BuzzFeed. “It is too difficult to define and parse what is ‘appropriate’ versus ‘inappropriate’ drinking in the office,” he wrote.

Apparently this distinction was a hard one for Zenefits employees to draw. On Monday, the Wall Street Journal got its hands on another staff memo, in which the company’s director of workplace services told staff members they were going to be shut out of their building’s stairwells, which were being used as makeshift love nests.

“It has been brought to our attention by building management and Security that the stairwells are being used inappropriately. . . . Cigarettes, plastic cups filled with beer, and several used condoms were found in the stairwell,” she wrote. “Yes, you read that right. Do not use the stairwells to smoke, drink, eat, or have sex. Please respect building and company policy and use common sense.”

It is clear that Zenefits is trying to sweep the red plastic cups and empty beer bottles now plaguing its image. But the good times seem to be over more broadly across Silicon Valley.

The start-up ethos has long been that anyone with a good idea, a pitch deck, and the willingness to shut themselves in a room with a computer for 15 hours a day could bring in a bundle of checks from prominent venture-capital funds chomping at the bit to get in on the next unicorn. But there is a new reality—one in which funding is drying up, markets are wobbly at best, and companies who rose to that billion-dollar valuation now face the possibility of down rounds.

The slowdown has cast a shadow over Silicon Valley in the last several months. Just 12 new V.C.-backed unicorns were birthed in the last three months of 2015, according to a report from CB Insights, compared to 24 in the third quarter. Deal-making activity fell to its lowest levels in three years, the report found, and V.C. funding tumbled 30 percent in the fourth quarter. A Wall Street Journal analysis found that 35 of the 48 venture-funded tech companies in the U.S. that went public since 2014 are now trading below their I.P.O. prices. It is no wonder, then, that December data from Ernst & Young shows that tech start-ups are now avoiding going public all together, likely fearing that same fate. Even companies that chose to stay private—including Zenefits and Snapchat—have slashed billions of dollars off their valuations in the last year.

It is a wake-up call that Silicon Valley of early 2016 is not the same place it was five years ago, or even 12 months earlier. But it does not feel like rock bottom—yet. Maybe a drink from that plastic cup filled with beer or a champagne shower is in order.