"Effective interaction with the player is an unsolved problem, and even the biggest companies struggle to innovate and push the boundaries," explains Robin Baumgarten, developer of the one-dimensional, easy-to-understand controllers called A Dozen Sliders. Here, he discusses a wide range of games he has made with very minimalistic slider input, along with how and why he built his devices, showcased at the brand-new alt.ctrl.GDC exhibit last month.

Thanks for taking the time to talk during your extended post-GDC voyage. I suppose let's start with the "why". Why did you build the sliders?

I'm a fan of local multiplayer games, and after making a successful local multiplayer game for Android that only uses a single button, I decided to make a sequel that uses a one-dimensional input instead of a (technically zero-dimensional) button.

While visiting a Wild Rumpus party in London, where local multiplayer games with often curious input methods are exhibited, I was inspired to make a similar controller + game combination myself.

How did you build the controllers?

When I first had the idea to make these slider controllers, I made a few prototypes out of plywood, using a selection of linear potentiometers (audio faders) with varying sizes and features. This happened late 2013, and I used my dad's wood workshop when I visited my parents for Christmas, using mostly spare cables and wood offcuts my dad had lying around.

I trialed the sliders on my relatives, and was encouraged by their positive feedback to submit them to alt.ctrl.GDC. They were accepted, and thus I decided to improve on them before GDC 2014. This coincided with me joining the London Hackspace (a community-driven workspace with loads of tools), and since they had a laser cutter, I decided to remake the boxes using frosted acrylic and add LEDs. I also chose a motor-driven fader that supported touch-sensitivity to make the controller more attractive.

The controller itself only houses the slider and the LEDs, and feeds back all information to a Teensy microcontroller, which is programmed on the Arduino standard, and can communicate with Unity using a serial port or MIDI connection. [Ed note: for more information on this, see Robin's presentation.]

Where did you build them, and where and when have they been exhibited?

I built the first wooden iteration with the help of my dad in late 2013, and the second iteration in early 2014 with the help of Maurizio Scuiar, who helped me with soldering and with programming during game jams. I used the sliders in two Game Jams (Global Game Jam '14 and the Train Jam), where I relied on the help of quite a few awesome friends to make games: For the Global Game Jam we made "Inslide World" (Geraldo Nascimento, Robert Ramsay, Antonio La Barbera, and me), and for the Train Jam we made "Monsterbation" (Maurizio Scuiar, Annakaisa Kultima, Mark Backler, Gorm Lai, and me).

Aside from using them during two Game Jams, the sliders were first exhibited at the alt.ctrl.GDC exhibition at GDC 2014 in San Francisco.

What can the controllers do besides rumble?

The motor in the Slider controller allows them to move to any desired position quickly, which can also be used to push and pull against the player. Since the motors in the sliders are fairly small, the exerted force isn't very big, but while the player can easily overcome the motor, it still enough force to surprise, aid, and (if desired) disturb the player.
This range of feedback is unusual in current-generation controllers, and can be used to elicit more interesting game-to-player and also player-to-player interactions.

Can slider-based games have depth?

While the input range is quite limited - touch and slide - I can definitely see potential for games with deep gameplay and meaningful interactivity. In fact, I don't think depth is necessarily linked to input complexity, and there are many examples of meaningful games with quite simple controls.

That said, my current focus in terms of style and depth for games that use the sliders is definitely more on the casual party-game side, which is a good match for a local multiplayer setting.

And what do you see as the possible breadth of games for A Dozen Sliders?

Most of the games I've made so far center around action-based multiplayer themes that clearly expose a single dimension as control scheme. In these games, where each (of up to currently 8) players controls a single slider, the focus is on quick competitive or cooperative gameplay. For example, a cooperative game was made during the Global Game Jam, where the players work together to influence time of day, era (past, present or future), and gravity to guide the game character through challenges. In another game, teams of two players control monsters in a rowing-boat style fashion to kill the opposing teams using carefully aimed broadside shots. Prototypes of other games involving a multiplayer-pong, a lightcycle race, a flappy bird-like game where each player controls a single pipe, an estimation quiz, and more have been made.

Cooperation with other indies has already led to a successful integration of the Sliders with the indie game FadeOut by Sujan McGlynn.

The style of the game is mostly limited by how easily the input can be mapped to a single (or a series of) linear intervals. There is also no reason why the game would need to be multiplayer - games where a single player controls a series of levers can also be conceived.

Why is it important to give these hardware experiments attention?

Effective interaction with the player is an unsolved problem, and even the biggest companies struggle to innovate and push the boundaries. Examples such as the Kinect and WiiMote show that companies are willing to take risks, and how difficult it can be to come up with sensible and easy-to-understand control-schemes.

Physical feedback to the player in particular is especially problematic, and there are very few solutions besides rumble and the occasional steering wheel force feedback. More experimentation is needed in that area, and it's one of the reasons why my Slider controllers contain articulated feedback.

And what do you think about the standard of controllers on current game systems?

Most of the successful current game control schemes center around efficient player-to-device communication and have converged to few schemes: mouse and keyboard on the PC, gamepad on XBox and Playstation, touchscreen on mobile devices. The highly optimized efficiency of those will make it difficult for any innovation to fully replace those - possibly Virtual Reality helmets can be one of those disruptors.

The Wii and WiiU systems employ more interesting controllers, as they play with more experimental movement interaction and second screen controllers.

[If you are making an alternative controller or device, be sure to reach out to alt.ctrl co-creator and IndieGames EIC John Polson. For other alt.ctrl stories, read here.]