This past Saturday afternoon, in New York City's Union Square, thousands of bubbles ascended beyond a small, pulsating crowd of 4,000. The "Bubble Battle" event was a celebration for 15-month-old dating app Happn, which hit four million users in early June. 

Founded by a trio of Frenchmen in March 2014, the app has since done well for itself. It quadrupled the number of users it reportedly had in December, having expanded into the U.S. by way of New York City last September and San Francisco as recently as March. It secured $8 million in a Series A funding from investors like DN Capital.

How does the app work? If someone catches your eye on the sidewalk, you use the app to "heart" them secretly. If they like you back, you'll see a notification: "It's a crush." And, if you really want someone's attention, you have the option of sending them a "charm." Males be warned: You'll have to pay a small fee--$1.99--to send out more than 10 charms to women.

One explanation for the fee is that men are usually easier to entice onto the platform (they make up 60 percent of users, with women accounting for the remaining 40 percent). On the assumption that men typically make the first move, there's "kind of an elegance," explains Rappaport, in keeping all of the app's features free for women. 

While critics have noted that Happn is something of a "stalker's dream" that could pose a threat to a user's personal security, the company says its privacy settings have been sufficient to keep people happy. For example, users have the ability to flag or block others.

Rappaport says he created Happn to fulfill a gap he saw in the dating app marketplace. "Past dating websites have been [built on] a kind of lie," he told Inc. by phone. "We all know that we will never find love because we have checked the right boxes. We will find love at the moment we don't expect it."

Enter: Your GPS. With Happn, users scroll through profiles they pass in real-time--within a 250-meter radius. The significance of the locations is that it can reveal a common interest, such as an art gallery or an indie movie theater. A user's most recent "missed connections" will appear at the top of his or her feed. Unlike Tinder, no swiping is involved. 

Rappaport says he's in talks for another $10 to $15 million in a Series B round that will mostly fund marketing efforts. Customer acquisition in an admittedly crowded market, which can be especially expensive in North America, is his number-one challenge. Tinder, for reference, clocks 50 million monthly users, and while Hinge hasn't disclosed its numbers, the app's user base reportedly grew by a factor of five in 2014.  

Saturday's "Bubble Battle" drew more than just your average flock of twenty-somethings: Small children and families also participated in the fun, with many stopping to picnic beyond, or to snap selfies with a new friend or paramour. I, for my part, befriended two German singles, who were lured to the park less by the possibility of true love and more by the probability of a free bubble gun.