This month, all the hip mobile gamers are rallying around Threes, a beautiful indie puzzle game that may be the unholy offspring of Sudoku, Dots and Rush Hour.
Since it launched on Feb. 6, Threes has dominated the iOS paid download charts, especially on iPhone, and even cracked into the top-25 grossing chart, where free-to-play titles reign. A big part of the game’s appeal is its deceptively simple design; minimalist numbered cards may be slid around the board and combined to make bigger numbers, as demonstrated in this GIF:
But the game wasn’t always like that. Co-creator Greg Wohlwend says he and his partner, Asher Vollmer, spent at least six of the game’s 14 months in development experimenting with the design, eventually working their way down to the “elegant” final product.
At one point, walls would pop up on the board that blocked players from merging cards in certain directions. At another, there were no numbers on the cards but instead symbols, like rolls of sushi or hydrogen and oxygen atoms.
For a time, Threes also had a monster that would wake up and eat numbers if it got hungry, Wohlwend said.
“I really liked the monster,” he said.
The idea behind all this was that the game needed a mechanism to stop players from thinking it too easy, sort of like how the blocks in Tetris fall at faster and faster rates as time progresses. A lack of obstacles, they feared, would make the game easy to quit.
“If the game isn’t compelling enough to hold someone’s attention, then the game needs to be better,” Wohlwend said.
Rather than starting out with a game that fit the “learn it in a minute, play it for a lifetime” tagline, Wohlwend and Vollmer worked their way down to minimalism after finding in testing that the number-sliding alone could hold players’ attention without gimmicks.
Also evolving over time were the characters. Almost all of the number cards in Threes have personalities: 3 is a wide-eyed child, 6 is a chill bro who says “sup,” 12 more excitedly greets players with “oh, hey!” and so on. They have faces along their bottom edges, but Wohlwend said those faces once dominated the whole card.
He shared the following screenshots from the game’s development — a glimpse into what might have been.
Threes is currently only on iOS, but Wohlwend and Vollmer say an Android version is likely in the future. They started with Apple’s devices because fragmentation on Android makes testing harder for a two-person company like theirs, Sirvo LLC. In the meantime, an unofficial sort-of-knockoff, Fives, is available on Google Play.
This article originally appeared on Recode.net.