Inside Bloons, the multimillion-dollar tower defense empire built on monkeys

You might expect to have heard of a developer that was bought three years ago for $142 million—a studio that’s existed for almost two decades with a community so dedicated they’ve built over a million user-generated levels. But Ninja Kiwi, the team behind the Bloons Tower Defense (or TD) series, isn’t often written about in articles like this one.

CEO Scott Walker reckons there are a couple of reasons for that. First, there’s the fact that the studio’s staff is split between Auckland, New Zealand and Dundee, Scotland—far removed from global hubs of media and game development. It’s a situation that tends to suit its developers, who are “pretty content” to fly under the radar. Second, there’s Bloons’ roots in casual, homebrew Flash games. “It’s hard to be taken seriously by AAA-focused journalists,” says Walker.

Yet those same roots are precisely why Bloons is beloved by so many—and worth so much.

Back in the mid ‘00s, the internet was flooded with browser-based gaming portals like Newgrounds, Kongregate, and Miniclip. Unlike the PC and console releases of the time, the games on these platforms were accessible in a matter of seconds. And so long as you didn’t mind subjecting your eyes to intrusive banner ads, they were free—a relative rarity in the years before iOS and microtransactions.

Many of these Flash games were throwaway, like the 2D recreations of snooker or skateboarding that just barely held people’s attention between pings on MSN Messenger. But others, like the backflipping motorcycle sim Trials and the sadistic platformer Meat Boy, had a lasting impact on the medium, inspiring other designers to build brutal-yet-forgiving games with high levels of difficulty and the ability to instantly reset levels to try again.

Then there was Bloons, the invention of brothers Stephen and Chris Harris. Released in 2007 (relatively late to the movement), the first game in the series was as simple and immediate as they come. Like the classic artillery games of the early ‘80s, Bloons merely challenged players to govern an object’s trajectory—in this case, a dart passing through a cloud of balloons just begging to be popped.

It was deceptively gripping. “The basic physics of impelling a projectile to hit an initial target is compelling enough, as it engages both angle and power, which creates a wildly complex set of options for which there are often multiple successful options,” Walker points out. “That trajectory is engrossing—but more so is what happens after that initial shot, as the player gets to see what happens to the rest of the Bloons after the first one has been hit.”

Bloons found an audience, and the early Ninja Kiwi team began answering demands for more levels. Some were easy, some hard, and some “played out like a Rube Goldberg machine. Failing a level was never a barrier; it was simply a try-again moment.”

Soon Bloons reached 100,000 players a day. Afterwards, the balloons and the darts—not to mention the monkey that threw them—became tenets of a carnival-esque universe that spun out into different genres. “Legend has it that Stephen’s wife Roseanne suggested that monkeys should be involved,” says Walker.

Most notably, Bloons became a fixture of the booming tower defense genre. Unlike many of its peers, Bloons TD trusted players with free placement of their defenses, in line with traditional RTS games. The balloons themselves turned out to be an unexpected boon—their different colors proved ideal for indicating hit points and special properties amid the chaos and motion of a typical tower defense map.

Several hugely popular Bloons TD sequels followed, alongside a number of other Bloons entries and spin-offs—not all of which have offered the same strategic depth. “We have to admit that Hot Air Bloon is one of our low moments,” says Walker.

But Ninja Kiwi has rarely lost track of what makes Bloons pop. While the studio’s art teams have been given more and more freedom to deviate from the 2D carnival style of those early Flash games, Ninja Kiwi has never sought to overexplain the fundamentally daft concept at the heart of the series. “The sheer ridiculousness of a monkey-centric world that is constantly fending off unending waves of Bloons without a grand Manichean story is pretty important to us,” says Walker.

That makes it easy for fans to join in. Since the beginning, Ninja Kiwi has released design tools to its community—a big factor in its continued success. “Once we had an editor for Bloons that allowed anyone on our small team to build levels for the game, sharing with players felt like the logical next step,” says Walker. Pretty soon, there were over a million player-made levels in the wild, and Ninja Kiwi was curating Player Packs to show off the finest examples.

While Bloons games are intended to be easy for a casual phone audience to pick up, Ninja Kiwi publishes detailed balance notes with each update. That’s because a hardcore base hangs on their every word and invests in scraps of monkey lore. “Bloons fans are incredibly, humblingly positive and supportive,” says Walker. “While they have no shortage of suggested ideas and improvements, they are very understanding of why we can’t do everything all at once.”

The team continues to push out big updates for Bloons TD 6, and is in the process of expanding its map editor into a game editor. That’ll enable mod-like control of towers, projectiles and modes, “so players can effectively publish their own game within a game.”

By now, it’s obvious that Bloons has one thing in common with its monkeys—a surprisingly long tail. What started as a browser-based distraction, a momentary flick from one tab to another, has long outlived Flash itself. And if Ninja Kiwi get its way, Bloons will persist long after we’re gone.

“We crossed a generation already with Bloons, and old school players share stories about now playing the game with their kids,” says Walker. “We’ve always said we want the Bloons brand to be around and recognized for the same great gameplay and positive community by our grandchildren.”

Bloons TD 6 is available on the Epic Games Store.