Interview: Popcap's Johnston On Plants Vs. Zombies' Tricky XBLA Shift

Popcap senior producer Matt Johnston tells Gamasutra about the game design intricacies of switching Plants Vs. Zombies -- "a game designed around mouse clicks" -- to Xbox Live Arcade.
The tremendously successful 'tower defense' hybrid Plants vs. Zombies isn’t the first Popcap game to make the transition from the PC to Xbox Live Arcade. But while both Peggle and Zuma had control schemes that lent themselves naturally to an analog control stick, senior producer Matt Johnston says the team behind the Xbox 360 version of Plants vs. Zombies ran into some trouble converting the mouse-centric game to the Xbox 360. “Taking this particular game, a game designed around mouse clicks, and bringing it over to the game pad was something I was worried about at the beginning of the process,” Johnston told Gamasutra as part of an in-depth interview on the George Fan-designed game's console conversion. One problem in particular was collecting the game’s falling, sun-based currency, a process that’s as simple as clicking the mouse in the PC version but felt a bit onerous when guiding an on-screen cursor with an analog stick on the Xbox 360. After an internal debate, the team decided to added a generous sun-magnetism to the cursor, to make the whole process a bit easier. “Collecting sun is important, but we don’t want to make the game feel like work, especially on the console,” Johnston said. “Where a PC gamer may tolerate that a little bit more or consider that to be a little bit more interesting part of the game play, a console player may be a little bit more casual.” Simply navigating the playfield also proved tricky for the Xbox 360 controller. “The grid-based gameplay makes it really difficult for the navigation using an analog stick to feel good,” Johnston said, “because it’s just so low resolution and clicking around the grid feels very regimented and it’s not very fun to move around ... especially in the later levels, [which] rely on quick movement and being able to target and plant exactly where you want to go.” Luckily, one of the team members hit on a solution that combines a free-floating analog-controlled cursor with a frame that locks onto the game grid, for easy plant placement. “It’s a nice combination of accurate grid-based targeting and fluid analog movement,” Johnston said. “We spent a lot of time just trying to get that to feel right but I think eventually we got there and I think a lot of it was he had this great idea of how to do this.” Spending a lot of time on small elements like this is something Popcap prides itself on, Johnston said. In particular, he talked about how simply balancing the default lineups for the plant and zombie sides in the XBLA version’s new versus mode took a good three-and-a-half months. And it probably would have taken longer if the team behind the original game hadn’t been on hand to help. ‘[The original team] had already done so much meticulous work on balancing each individual zombie against each individual plant,” Johnston said. “Getting those guys involved and having them just play the game and say ‘That guy is a little too overpowered’ or ‘That guy is a little too underpowered’" "I think we would not have been able to get it as right as we did if those guys hadn’t been involved and if they hadn’t spent so much time thinking about what the effect is if you change the cooldown on something or you raise the price of something how it affects the balance, globally.” Popcap’s attention to detail even extends to relatively minor interface design cues, Johnston said, such as the co-op survival mode’s “double sun,” which requires two players working together to collect. “I feel so strange when I listen to myself describe some of the things that we do, but we sat there and spent a lot of time looking at how that double sun was going to look and animate, trying to second guess over and over and over again how somebody who had never played PvZ or somebody who may be confused by it, what they would think and what they would do.” “I guess we just spend a ridiculous amount of time on little stuff like that like all the time,” he continued. “I feel incredibly lucky to be working for a company that values those things and shares my need to sort of exercise my OCD and go through every little detail.” Such meticulous focus has its downside, though, as a development process that was supposed to take a year stretched on to nearly 18 months for the Xbox Live conversion. While Johnston says he empathizes with those who were upset with the long wait, he also thinks it’s important that the team “take the time to do things right.” The whole process could have taken even longer, though, if Johnston hadn’t decided to finally halt work on an online-enabled version of the versus mode. In testing, Johnston said the head-to-head online mode broke down online because users would feel an urge to drop out once the momentum had begun to swing away from them, ruining lots of careful setup work from the opposing side. “I know that that’s a reality in a lot of multiplayer games, but there actually very few online multiplayer games that have only two players in them,” Johnston said. “If there are ten people playing Halo and one of them drops out it’s not really a big deal, but if it’s a head-to-head game and somebody drops out after seven minutes, it just sucks.” While Johnson said that, in retrospect, he could have included the online versus mode as a way for friends to battle each other, by that point in development he wasn’t eager to mess with a single-couch co-op mode that was working well. “To be honest, getting that working and tested would have taken another six months, and it had already taken us so long to even get to the point where we even knew we were at this crossroads ... I didn’t feel like it was worth adding another six months to the schedule to get that right. ... At some point every good game developer has to decide, ‘OK, I’m actually gonna ship this game this year.’”

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