Written by Harry Krueger, lead programmer on RESOGUN at Housemarque.
RESOGUN is a fast-paced, explosive horizontal shoot 'em up that was released alongside the PS4's launch in November 2013. It was developed by Housemarque, a company that has been around for 20 years now, and published by Sony XDev Europe.
RESOGUN was in development for a total of about 20 months or so, with an additional 12 months added to develop the two expansions for the game: Heroes and Defenders. The core team was 12 members strong, with frequent support from our R&D and art departments, so in total about 20 people total worked on the original version of the game.
Voxels are essentially 3D pixels, and are quite literally the building blocks of the RESOGUN universe. At Housemarque, we've been making arcade-style games for a while now by marrying timeless gameplay values with cutting-edge tech. During the time of RESOGUN's inception, we were considering ideas for our next big game and voxels seemed like a natural way to express this "neo-retro" design philosophy. We quickly came up with a few concepts to utilize this aesthetic approach: one of them was a shoot 'em up, another morphed into an unreleased mobile game, and a few more never made it out of concept phase.
The name "RESOGUN" was coined by Petteri "Petsku" Putkonen, one of our guys at the time. The "RESO-" prefix touches upon the concept of high " RESOlution", and the "-GUN" postfix was added since -- being a shoot 'em up -- we predicted you'd occasionally be shooting things.
The pre-production process was rather simple: Before we started development we made a concept video of the game, featuring a rough estimate of what the visuals and gameplay would be like. I remember when Harri Tikkanen, our creative director, first showed the video to me; being a huge shoot 'em up fan I instantly recognized this as my dream project, and I insisted I'd work on the game if we went ahead with it. A few months later, development started.
Image taken from the concept video.
In the beginning we were fairly platform-agnostic. At the time we had PS3 and PS Vita dev-kits in house, so we used those as a reference for potential platforms. When considering possible multi-platform development though, the weakest platform always becomes the lead. In the context of our early development, this meant that RESOGUN was initially targeting PS Vita hardware, and all the technical possibilities and limitations that came with that.
We started implementing the game using the Super Stardust Delta engine. Since both games shared a similar design approach (being shoot 'em ups mapped onto a 3D surface), we were able to utilize many of the existing sub-systems and start working on the base version of RESOGUN immediately.
Preliminary concept art for an early version of the game.
Aesthetically, we started out on a somewhat lighter note. Initially we were planning on having brighter colors, blue skies, and a more naturalistic tone, to represent environments that we thought would be the human habitats. The first level we prototyped had a huge tree in the background, and the humans were in small huts. We eventually shifted away from this and went for a darker tone.
For the gameplay, we knew from the start that we wanted a horizontal, fast-paced, skill-based shoot 'em up. We've been largely inspired by classic arcade games, and we wanted to do our part in keeping that arcade spirit alive. Our goal was to achieve that "one more go" feeling, and create a game that's easy to pick up and hard to master. "Depth without complexity" was a mantra we followed; allow the main game to be simple to pick up and play, but create some layers of depth for those looking for that extra challenge.
Adding some humans for the player to save worked well with this approach. Much like Defender and Datastorm (two of our key inspirations), introducing this extra gameplay layer of saving the humans created an interesting tension for the player, as they needed to balance their "shoot and survive" abilities with a clear secondary goal. We adopted the human-saving mechanic from our very early prototypes, and the humans ended up largely defining RESOGUN's identity.
Another thing we knew early on was that RESOGUN's gameplay would take place on a cylinder. When having a horizontal looping playfield in a purely 2D environment, some kind of minimap is essential to communicate the extended surroundings to the player. Mapping RESOGUN's gameplay to a cylinder eliminated the need for a minimap, as the player can always see around the bend and plan ahead. This helped instantly create intuitive gameplay, and from a visual standpoint the cylinder also made RESOGUN stand out even during early prototyping stages.
Image from an early prototype version.
One other key aspect of RESOGUN was of course the use of voxels. Due to our technical constraints at time, early versions of the game merely simulated the voxel look through carefully constructed meshes and particle effects. Originally we had also envisioned the voxels playing a larger, more direct role in the gameplay. We intended to have the player pick up and manipulate voxel objects, and maybe shoot them towards the enemies. During very early prototyping we realized that this careful voxel management would conflict with the intense arcade action we were shooting for, so we quickly abandoned the idea.
In hindsight, it's actually really hard to differentiate between the development of "the prototype" and "the game." You can easily hack together a working prototype in a couple of weeks, and then proceed to spend two years continuously refining and polishing it to perfection. With RESOGUN, we aimed to create something unique from the start, so we attempted to innovate from very early stages of development, which led to a lot of different iterations.
When looking at a finished game, everything often feels effortless and naturally integrated into the final product. However, reaching the end result is usually a process of "natural selection" where countless features are eliminated and very few make it into the final cut. At Housemarque, we subscribe to the common game development notion that it's better to iterate and fail quickly. We try to test simple versions of ideas immediately, and then let the game decide: If it works, we keep and refine it, and if it doesn't we discard it and move on.
Below are some of the many ideas we tried for RESOGUN that didn't make it into the final version:
The Tower: We knew from the beginning that we'd require some kind of "drop off point" for the humans. Initially we experimented with a tower-building mechanic, which would collect humans and grow over time. One version had the player collecting all the humans at the tower, and the humans would then run around on a treadmill to generate power ups for you. Outside of feeling a bit abusive towards the humans, as a gameplay mechanic it also felt unnecessarily complicated and hard to communicate.
The Weapon Shop: By killing enemies and saving humans throughout the level, the player would collect "orbs" which functioned as an in-game currency. At the end of each phase, the weapon shop would descend onto the playfield and allow you to exchange your orbs for weapon power-ups. Although the actual implementation was great (it even allowed you to preview items before purchasing), it severely affected the pacing of the game: just as the intensity was ramping up and the player was getting into the zone, we were pulling them out of it and asking them to decide on weapons purchases. Unacceptable.
The weapon shop was one of many ideas we tried but ultimately abandoned.
The Weapon "Options": For the weapons, we also tried having some Gradius-style "options" (helper ships that assist you by shooting alongside your main weapon) which sported a variety of different weapons. The Options didn't work that well with the relatively confined shooting gameplay we were going for, so we went with traditional power-ups instead.
The World Map: We were originally planning to have 10 levels in the game, and had an ambitious plan to incorporate a world map to connect them with each other, hoping to lend the game more cohesion and structure. In between levels the player would get thrown onto this world map, where they'd select the next level from multiple routes. It was unnecessarily complicated, and we ended up discarding it because, once more, it affected the intensity and flow of the experience.
One of the many concept renders for the "World Map" we tested.
The Humans: We had lots of different iterations over the humans. Originally we had humans that would be easily killed by enemies' bullets, and eventually even by the player. Later we iterated over humans with an extra glow or ring around them, to indicate what kind of power up they'd give you. We even tried having special "scientist" humans that award you with power-ups, while the "normal" humans wouldn't.
All of this was once again difficult to communicate and hard to keep track of during gameplay. Initially humans would also spawn from their own "huts", which we would burn to the ground before releasing them. We shifted away from this and trapped them as prisoners in "human chambers" instead, where they'd always be visible to the player.
Originally we had humans escape from their burning houses.
360-Degree Shooting: This is an interesting one. When we got the first prototype of RESOGUN running we naturally tried 360-degree shooting as well, just like Super Stardust HD had. Shooting in 360 degrees generally allows the player more freedom, and this encouraged a more passive play-style that basically transformed the player into a "moving turret": you'd move to a safe location, shoot around, move somewhere else, shoot around, and so on.